Possibly, but the load you are controlling could also be causing the "can't turn off" issue. If you have a noisy load (fluorescent lights as I experienced) then the turn off and turn on can be different causes but related.
I suppose it's
possible that the load could interfere with the module's operation. (In the case of one of these failed XPS3 modules, it was necessary to add an incandescent bulb to the load side (along with its "normal" florescent shop lights load) in order to get the XPS3 to work properly via PLC when initially installed). But, in general, load issues don't seem to "track with" all the circumstances of these failures. For instance, in all cases, the modules worked with their respective loads for some time (maybe for
years in most cases) before the common malfunction occurred... and the failed modules controlled assorted types of loads yet all suffered a common failure mode. Also, all replacement modules worked (so far) with the original load circuits.
I didn't think to disconnect
only the loads before replacing the failed modules - but I did "bench-test" each of the failed modules while loaded only by either a single incandescent bulb or by a single LED bulb, and got the same results as existed when the failed modules were installed (where they controlled assorted types of load circuits).
So, it
appears that something other than the respective load circuits was responsible for the flurry of common failures.