UserAgent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/62.0.3202.89 Safari/537.36

Steps to reproduce the problem:
1. Compose new email (Google Apps / Gmail)
2. Click the "Insert files using Drive" button
3. Select a file with extension ".STEP"
4. Change Insert as type to "attachment"
5. Click Insert.  nothing happens.

What is the expected behavior?
Expect the file to be added as an attachment to the email.

What went wrong?
This works in Chrome 61.0.3163.100 (Official Build) (64-bit) but not in Version 62.0.3202.89 (Official Build) (64-bit).  You can also attach the same .STEP file using the paperclip "attach files" link in the compose window, as well as you can use the "Insert as - Drive link" option when inserting files from Drive, you just can't attach the actual file as an attachment.  At the same time, you CAN attach other types of files, such as PDF files.  This almost seems like this version of Chrome does not like to attach .STEP files from Google Drive.  A sample file is attached.

Did this work before? Yes 61.0.3163.100

Chrome version: 62.0.3202.89  Channel: stable
OS Version: 10.0
Flash Version: 

User accounts are GSuite accounts.  No other changes have been made.  Firewall is not blocking anything...issue was narrowed down to being the version of Chrome after testing on two separate networks between multiple user accounts and computers.
 

Deleted: StepBucktest1.STEP 24.2 KB

StepBucktest1.STEP 24.2 KB Download