GOOD NEWS: ... if that's the case, that's some good news. It simply means that you have to wait until Jolla releases an update of Sailfish X that uses the slightly newer kernel and firmware that your Xperia X had right before the upgrade. Or even better the upcoming kernel 4.4 that Sony is preparing as part of their Android 8.0 Oreo efforts.
All I can recommend right now is that you get in touch with the Jolla customer service (and mention this post or the one on TJC) so they can take a look at this issue.
I second that, opening a ticket on Zendesk would be a good idea.
specific type of cards ("SDR104, HS200 and HS400 cards and if clock frequency is greater than 100MHz in these modes.")