I’ve never used the Recording feature, either FM or Voice on any of my players so I can’t suggest anything but to possibly manually install a previous version of firmware to see if this issue is version-specific. Yes, it’s strange that 1 player works fine, but 3 others do not, even with the same firmware version.
But it would only take a few minutes to test this out, and if you find that the recording feature works fine in a previous firmware version, that would be helpful to the SanDisk dev. team (and ultimately all users) as they could figure out what ‘broke’ the feature in this latest release.
You could try 01.01.20 or 01.01.18.