Not sure how to accurately discribe this issue. I got this issue report here on my mod oritech: Rearth/Oritech#217
which relates to the transaction API. There, an oritech fluid pipe (which uses FFAPI) is used with a tesseract (neoforge-native block entity), which then forwards the transaction call to another fluid pipe. Because it doesnt actually accepts the insertion transaction first, but instead directly moves the content along, a new transaction is created before the first one is closed. More details and logs can be found in the original issues:
SuperMartijn642/Tesseract#105
and
Rearth/Oritech#217

It looks like this is still an issue on Forgified Fabric API 0.107.0+2.0.24+1.21.1

https://pste.me/@mSnHohjaJgw

Hm, I'll check when I get back later. Any chance something went wrong with the release/upload process @Su5eD ? The line numbers in the crashlog indicate that it's not using my changes, and instead point to the line with the issue from before my change.

If the version is correct, the code should match, too. The release pipeline uses a clean checkout so this shouldn't happen. We'll probably need to look inside the jar