azure is always updating its data centers. its a rolling update, so not all server are updated at the same time. in general the update does not break anything. but because you are running unsupported software, you are basically on your own to determine the issue.
your best option is to upgrade to a supported version. core
note: 2.1 was the only version that supported 4.* assemblies. you will need to replace the dependent assembly with a .net standard or core version.