Yes, I have been turning off the calculator between testing writing and reading.
However I have some more data and now suspect that it is a recording issue.
I had forgotten that I had one pre-recorded card - the HP diagnostics - in my possession. That is a two sided card that prompts you to flip it over. I tried several times to read it and execute it and every time it succeeded and ran the diagnostics as expected.
With the diagnostics program loaded from the prerecorded card, I recorded it to a blank card. When I tried to read that one after powering off the calculator, it gave an error. One time, I was able to get it to read without an error, but the program did not execute successfully.
So, I decided that it seems to be a recording problem since reading the prerecorded card seems to work OK.
I had received a pack of cards with the calculator. I thought I would try a different card when I realized that in the pack was an abrasive cleaning card that I had not seen before.
I ran the cleaning card twice through the calculator (I do not know what the manufacturer actually recommends).
I loaded from the prerecorded card, then recorded to the same blank card I had been trying before. And, lo and behold, it read and when I executed it ran the diagnostics as expected.
So, I guess it was a recording issue after all.
So, now my question is this. The abrasive card seems to have improved the situation. I am reluctant to use it often. Is there some other cleaning procedure (deoxit?) that I should use to get everything working as best it can?
Edited: 9 Dec 2013, 7:01 p.m.