I have one HP-25C that exhibits a lack of programming storage, for example entering any key code in program mode results in <01 1 00> in run mode the unit stores and recalls correctly, also using Sigma+ works correctly.
I have kept the unit running without any signs that would be indicative of the clock skewing issue. I haven't tried putting a 20K resistor across data line 11 and ground though.
Is this a problem with the ACT or RAM IC?