If you encounter any hanging/unresonsiveness issues with YAACARS, try to:
It seems that this aircraft uses internal fuel tanks. Only default LEFT MAIN and RIGHT MAIN are used and visible to YAACARS
Might still be a bug - didn't investigated further. Found on the web: https://fsuipc.simflight.com/beta/Offset_Mapping_PMDG737NGX.pdf Acoording to this document, the 737 has LM/C/RM tanks, but also it's own datarefs to read the tanks …
From version 2.0 on YAACARS detects “refuelling” and “defuelling” so your fuel tanks (in FTW) will be empty within a very short time!
⇒ try to start the flight in YAACARS after the APU has been shut down and finish the flight before turning on the APU back on