I have been having the same problem and, having now read this thread, it is apparent that the problem is endemic. So a few thoughts and questions :-
1. Is it HMRC or DWP that are assuming the erroneous triple lock increases? DWP told me twice (in phone calls) that it is not them. My feeling is that it is HMRC that are instigating the problem but I'm not sure.
2. Is there anyone here whose SP is frozen and the correct amount is reported by HMRC in their Gateway a/c and they did not have to contact HMRC or DWP to correct it? In essence, does the system work properly for anyone?
3. Imo freezing our SPs is morally, and possibly legally, wrong. HMG expect us to be honest and tell them where we live so they can freeze them whilst we are having to pay tax on non-existent increases. So if anyone decides to inform DWP that they are relocating back to the UK when they are not then who can blame them? If they happen to be caught out doing this then the mitigation in any very unlikely court case would be "well you're taxing me as if I am back in the UK".