@Andrey Yasko ,

Differences in coding patterns, yes. That is a major issue. There is also the factor of loss of interest for whatever reason, where a vendor just quits and won't update or upgrade the module. What happens is that the system becomes incompatible, leaving one hanging dry.

This is why I had to make a hard decision to not purchase any third party modules, no matter how useful they are.

The Internet is constantly shifting too, something which is beyond the control of UNA or any other software vendor. That means changes must be made once the main developers decide to move with the time, and there is no guarantee that third party systems will readily move along.