If 2.0.4.17 fix refers to “* Fixed an issue where index files were not generated, thanks @seantempleton” then it fixes a bug that got in 2.0.4.16 with new parallel upload code, so that was a rather temporary issue and probably wouldn’t help any older releases. For any who found the issue here to get worse in 2.0.4.16, code here might have been rebuilding the missing index files while still displaying PreBackupVerify phase which is one of two phases that show “Verifying backup data”. It helps when reports describe error timing.
Rebuilding an index file appears to get logged if at Information level, as seen in text from bug report above, or from the earlier post in this topic, which also very clearly says PreBackupVerify so reduces guessing. This “Re-creating missing index file” isn’t new, but not all of the reports here have info needed to identify it. Not every little action gets its own phase, so guesswork may be needed on what code caused an issue…
Does that mean that it’s an intermittent slowdown? I notice most reports don’t say much about frequency.