DDNS-script are stopping randomly

I am running ddns-scripts inlcuding luci-app for years and just recently it appears that they do stop responding and I cannot figure out why and when. Any idea on how to debug?
Once I do restart ddns again everything works fine for all dynamic dns targets but then it stops again...no idea why. Nothing in the logs that I could find by now

How to debug?

currently running wrt1200 ac with latest snapshot:
Model|Linksys WRT1200AC
Firmware Version|OpenWrt SNAPSHOT r13527-61307544d1 / LuCI Master git-20.160.76921-16f443b