It could be the control board in the PD52 or the fact that the control board does not like the voltage or cycles from the generator. Relays fail a lot less than electronics. I good test will be to plug into shore power and see if the control board pulls the other replay to power up the trailer.
For now you could bypass the PD52.
https://www.rvsupplyparts.com/catalog/rv-automatic-transfer-switches/progressive-dynamics-50-amp-automatic-transfer-switch-pd52v-7383.html This document has some trouble shooting and instructions on disabling the time out function.
https://www.progressivedyn.com/pdfs/110537A-English.pdfChris
