It was all working fine and easy for him to use. Has anyone else had experience with this kind of problem?
Yes, but with Appliance Modules.
I have them come on when we have a brown out. When the power comes back up slowly or flickers before stabilizing, I have appliance modules clicking ON all over the place. It used to be such a big problem with the old brown modules that home control systems of the early 90s (i.e. Enerlogic, JDR, etc) had a power restore feature where you selected the state you wanted your modules placed in after the power stabilized. X10 made things much better by adding MOVs to the later single board design.
As Brian notes, it could also be the "Local Control" being falsed.
Either way, when I have a device I can not risk having turn ON accidently, (i.e. a 1950's 120V air raid siren which can be heard from blocks away) I run two Appliance Modules in series.
In your application you could plug an Appliance Module in to the SR227. The only problem is: obviously the SR227 must be turned on first and the appliance module is turned on second. To turn off, maintaining the double protection, the Appliance Module must be turned off first and the SR227 turned off second.
This double module will also stop the problem if the accidental ONs are caused by the Local Control.
Also your friend might consider using a CM15A and AHP to twice a day send OFF commands to all X10 modules when the cabin is not occupied. He could also make macros do all the necessary sequence commands to the SR227 and Appliance Modules rather than having to send multiple commands it over the phone.