pattrstorage "incompatible file type" and asking instead of saving

I have a Max patch that used to run flawlessly. It has two pattrstorage. Startup reads the two files. Saving uses "writexml". Haven’t used this patch for a while, I guess 3 or 4 minor Max upgrades.

Now it makes problems:

1. At startup, the console often says
"pattrstorage • incompatible file type"
The message went away for a couple of hours, now it is back again.

2. When the patch wants to save the pattrstorage contents after clicking the respective button, the save dialog appears. This should not happen. Sometimes only once (for both saving actions), sometimes for both actions. This behavior went away for a couple of hours, now it is back again.

I saved and closed the patch several times.

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What could be the cause for this change in behavior, could it be related to some of the recent Max updates?