@masc Welcome to the party!
I know exactly what is causing this, I have SanDisk Extreme Pro 95MB/s 32 GB SD card which doesn't work at high OC (192 MHz and 240 MHz) when applying SDR104 patch, only 160 MHz works with SDR104.
I made some benchmarks in the past in PC using many card readers and it benchmark at ~45 MB/s which mean more likely PC card readers is using SDR50 mode for that card or SDR104 mode but at low frequencies (below 100 MHz).
However, by using SDR50 mode on camera (disabling SDR104 patch) and applying high OC like 192 MHz and 240 MHz, my SanDisk Extreme Pro 95MB/s 32 GB *works fine.
*(not stable at 240 MHz though, drops after some time to 21 MB/s, this issue is not related to the new sd_uhs).
That's a little weird, according to SD Association SDR104 mode should be used for frequencies higher than 100 MHz (~50 MB/s).
SanDisk Extreme Pro 95MB/s 32 GB is weird on its own ways (at least for the one I have) . .
New
Universal SD Overclocking module version for
DIGIC 5 models:
Universal SD Overclocking module - DIGIC 5.zip-Added
Access Mode toggle setting:
You can select SDR50 or SDR104, SDR104 is selected by default which should work on all recent fast SD cards.
Only try SDR50 when SDR104 fails. Like in SanDisk Extreme Pro 95MB/s case.


You need to restart the camera after changing this setting.
You can find this setting in SD Overclocking submenu.
-Also added
EOS M2 1.0.3 support, to be tested.
@masc
Your SanDisk Extreme Pro 95MB/s 64GB might be stable at 240 MHz (might not drop to 21 MB/s after some time like my SanDisk Extreme Pro 95MB/s 32GB). Give it a try!