Premiere Pro 2020 audio issue

Just upgraded to Premiere Pro 2020 today and issues with my sound. Particular sound files (with effects applied) don't play back when I preview. The majority do, but not all. I have other similar sound files, from the same recordings (with exactly the same effects) that play back perfectly. I restarted and deleted the cache. But still those particular files won't play. If I uncheck the effects they play. Hate to think how many other files won't play - as this is a long movie project with lots of sound files used.

Wanted to go back to CC2019, but Premiere doesn't allow that.

Any thoughts on the sound issue?