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