When you use -m you run the risk of losing some information, but it is likely that the information was corrupted to begin with. I have added a new FAQ to help with this question.

I suggest looking at some of the images that are giving you errors. Try using exiftool to extract all information (with -a -u -G1) before and after editing with the -m option, then look at the differences to see what information, if any, was lost:

A couple more comments about what you are doing:

1) Dates set by -alldates should be in the form "YYYY:MM:DD hh:mm:ss". In your example, you leave out the time.

2) The -d option has no effect when writing, so you can remove this from your command.

3) Any image that produces an error when writing will not be written, so applying the same command again should have the same effect. I don't understand what you mean by "f I keep trying it is done afterall" in this context.

4) The date/time shift of +1 hour must be done in a separate step after writing the date/time values.

- Phil