“did you mean they were not replaced with Ultra Fit? Any chance to share what is the repalcement model which works well?” - SanDisk Ultra USB3 64GB, I did not chose the model, but specifically stated that I do not want a microdrive anymore.
“would you mind to share what is the average write and read speed you can achieve with the replacement model?” - a quick test shown ~100MB/s sequential read and ~50MB/s sequential write. While not great, but it is fine - also the flash drive remains barely warm with a load that killed the UltraFit (copying to flash drive a VHDX disk image of size ~10GB).
I am happy now with the “quality for price” I got with these new drives.