It’s really hard to give advice without seeing a log of the error. I’m not aware of any concrete conclusions one could take from just knowing the tx_retries count. The value of other stats leading to the error would likely be more informative (and changes in tx_retries would likely only be useful in comparison to changes in those other stats).
Separately, there have been recent reports of issues with stm32h7 mcus in “usb to canbus bridge” mode - Micro-controller timing tuning and fixes by KevinOConnor · Pull Request #7128 · Klipper3d/klipper · GitHub and 'Timer too close' after CANbus conversion - #18 by nefelim4ag . It’s hard to say if what you are seeing is related.
Cheers,
-Kevin