Password manager internals logging:

Captured password manager logs are listed below. Logs are cleared and no longer captured when all password-manager-internals pages are closed.
Message: PasswordAutofillAgent::DidStartProvisionalLoad 
The new state of the UI: 0
Message: PasswordAutofillAgent::SendPasswordForms 
only_visible: false
Security origin: https://twitter.com/ 
Number of all forms: 11
Form is a password form: {
Action : https://twitter.com/ ,
New password element : user_password ,
Origin : https://twitter.com/ ,
PSL match : false,
Password element : current_password ,
Password generated : false,
Scheme : HTML ,
Signon realm : https://twitter.com/ ,
Times used : 0,
Username element : 
}
Message: PasswordManager::CreatePendingLoginManagers 
SSL errors present: false
IsPasswordManagementEnabledForCurrentPage: true
Number of pending login managers (before): 0
Adding manager for form: {
Signature of form: 11260233611672432212
Signon realm: https://twitter.com/
Origin: https://twitter.com/
Action: https://twitter.com/
Form name: password-form
Form fields: 
current_password: 2036825362, password
user_password: 139615506, password
user_password_confirmation: 387786699, password
}
Message: FormFetcherImpl::Fetch 
FormFetcherImpl::state_: 1
Number of pending login managers (after): 1
Message: Generation invalid PasswordForm 
Message: Generation invalid PasswordForm 
Message: Generation invalid PasswordForm 
Message: Generation invalid PasswordForm 
Message: Generation invalid PasswordForm 
Message: FormFetcherImpl::OnGetPasswordStoreResults 
Number of results from the password store: 2
Message: PasswordFormManager::ProcessMatches 
SSL errors present: false
IsPasswordManagementEnabledForCurrentPage: true
Message: PasswordManager::Autofill 
wait_for_username: true
The new state of the UI: 3
Message: Generation invalid PasswordForm 
Message: Generation invalid PasswordForm 
Message: Generation invalid PasswordForm 
Message: Generation invalid PasswordForm 
Message: Generation invalid PasswordForm 
Generation possible account creation forms: 1
Message: Generation: no non-blacklisted confirmation 
SSL errors present: false
IsPasswordManagementEnabledForCurrentPage: true
Server predictions: {
Signature of form: 11260233611672432212
Origin: https://twitter.com/
Action: https://twitter.com/
Form fields: 
current_password: 2036825362, password
user_password: 139615506, password, SERVER_PREDICTION: NEW_PASSWORD
user_password_confirmation: 387786699, password, SERVER_PREDICTION: NEW_PASSWORD
}
Server predictions: {
Signature of form: 10487806070333104960
Origin: https://twitter.com/
Action: https://upload.twitter.com/
Form fields: 
status: 1245147674, textarea
: 1318412689, text
: 717494984, radio
: 717494984, radio
: 717494984, radio
: 717494984, radio
: 4203909268, select-one
: 4203909268, select-one
: 4203909268, select-one
: 1318412689, text, off
}
Message: Generation: no server signal 
Message: Generation: eligible form found 
Message: PasswordAutofillAgent::OnFillPasswordForm 
ambiguous_or_empty_names: false
Number of potential forms to fill: 1
form_data's wait_for_username: true
form_contains_fillable_username_field: false
username_field_name empty: true
password_field_name empty: false
Message: PasswordAutofillAgent::SendPasswordForms 
only_visible: true
Security origin: https://twitter.com/ 
Number of all forms: 11
Form found on page: {
Action : ,
Form name or ID : 
}
Form is visible: true
Form found on page: {
Action : ,
Form name or ID : 
}
Form is visible: false
Form found on page: {
Action : https://twitter.com/ ,
Form name or ID : 
}
Form is visible: true
Form is a password form: {
Action : https://twitter.com/ ,
New password element : user_password ,
Origin : https://twitter.com/ ,
PSL match : false,
Password element : current_password ,
Password generated : false,
Scheme : HTML ,
Signon realm : https://twitter.com/ ,
Times used : 0,
Username element : 
}
Form found on page: {
Action : ,
Form name or ID : 
}
Form is visible: false
Form found on page: {
Action : ,
Form name or ID : 
}
Form is visible: false
Form found on page: {
Action : ,
Form name or ID : 
}
Form is visible: false
Form found on page: {
Action : ,
Form name or ID : 
}
Form is visible: false
Form found on page: {
Action : ,
Form name or ID : 
}
Form is visible: false
Form found on page: {
Action : ,
Form name or ID : 
}
Form is visible: false
Form found on page: {
Action : ,
Form name or ID : 
}
Form is visible: false
Form found on page: {
Action : ,
Form name or ID : 
}
Form is visible: false
Some control elements not associated to a form element are visible: false
Message: PasswordManager::CreatePendingLoginManagers 
SSL errors present: false
IsPasswordManagementEnabledForCurrentPage: true
Number of pending login managers (before): 1
SSL errors present: false
IsPasswordManagementEnabledForCurrentPage: true
Message: PasswordManager::Autofill 
wait_for_username: true
The new state of the UI: 3
Number of pending login managers (after): 1
Message: PasswordManager::OnPasswordFormsRendered 
Message: PasswordManager::CanProvisionalManagerSave 
Message: No provisional save manager 
Message: Generation: account creation form already found 
Message: PasswordAutofillAgent::OnFillPasswordForm 
ambiguous_or_empty_names: false
Number of potential forms to fill: 1
form_data's wait_for_username: true
form_contains_fillable_username_field: false
username_field_name empty: true
password_field_name empty: false
Message: PasswordAutofillAgent::SendPasswordForms 
only_visible: false
Security origin: https://twitter.com/ 
Number of all forms: 11
Form is a password form: {
Action : https://twitter.com/ ,
New password element : user_password ,
Origin : https://twitter.com/ ,
PSL match : false,
Password element : current_password ,
Password generated : false,
Scheme : HTML ,
Signon realm : https://twitter.com/ ,
Times used : 0,
Username element : 
}
Message: PasswordManager::CreatePendingLoginManagers 
SSL errors present: false
IsPasswordManagementEnabledForCurrentPage: true
Number of pending login managers (before): 1
SSL errors present: false
IsPasswordManagementEnabledForCurrentPage: true
Message: PasswordManager::Autofill 
wait_for_username: true
The new state of the UI: 3
Number of pending login managers (after): 1
Message: Generation: account creation form already found 
Message: PasswordAutofillAgent::OnFillPasswordForm 
ambiguous_or_empty_names: false
Number of potential forms to fill: 1
form_data's wait_for_username: true
form_contains_fillable_username_field: false
username_field_name empty: true
password_field_name empty: false

+vabr as this might be even closer on the form parsing side.

This is a server side bug... the second password field (user_password_confirmation) should be of type CONFIRMATION_PASSWORD. This will be fixed by Vadym on the server.

Awesome, works for me.