It looks like when the backup is saved, the recorded keys are cleared, so that if you keep hitting repeat it shows
"No keys recorded. [Saving backup copy 'Dor.bak'. Please stand by.]"

It also happens if you take any other action that results in no turns passing: walking into a wall, trying to 'u'se from the tool slot when nothing is selected, going to the inventory and hitting z, etc. Eg:

You first should ready some tool. [Saving backup copy 'Dor.bak'. Please stand by.]
You first should ready some tool. [Saving backup copy 'Dor.bak'. Please stand by.]
You first should ready some tool. [Saving backup copy 'Dor.bak'. Please stand by.]

And just to clarify, it's not just repeating the message, it's saving the backup file over and over. And r56 is also affected.

Fixed. Also the recorded keys aren't reset anymore for backup saves.