We are seeing frequent, quasi consistent failures in PPAPINaCl tests in the  Linux ChromeOS Buildspec Tests builder:

https://uberchromegw.corp.google.com/i/chromeos.chrome/builders/Linux%20ChromeOS%20Buildspec%20Tests/

Note: That builder builds both 55 and 56 (Release and Beta).

Currently:
56 seems to be failing consistently in PPAPINaClPNaClNonSfiTest
55 has been passing, but did fail in build #1052 in PPAPINaClPNaClTest

There are no chrome changes between failing and passing builds that appear related.

Failures all appear to have the symptom "Plugin crashed. 'NaCl module crashed'"