for record - the problem was probably in using plpgsql_check together with PL debugger (plugin_debugger). Both extensions use the PLpgSQL DBG API, but this API is not designed to be used by more extensions. plpgsql_check has implemented some workaround, but it should be loaded last if this workaround should work. Older versions of plpgsq_check (without profiler) didn't use DBG API.