Hi all - please use this topic to post feedback specific to 2021.09. Release-specific feedback is valuable to us, and consolidating it in a single topic is extremely helpful. Thanks in advance!
2021.09 Release Notes
In addition to what Jon said, have you set your bounce buffer size to a high value? If so set it back to Follow Playback buffer size and retry.
Also you can easily disable the plugin flushing as mentioned in the release notes:
Edit > Preferences > Audio - Configuration File: BounceFlushTailsMaxDurationSec=n (0 to 60; default is 20; set to 0 to disable tails flushing)
Effects tails maximum flush length while bouncing (seconds).