I’m having the same issue as well, in Thessila. Cannot buy anything, because I cannot exit the menu after I’ve purchased! I’ve tried double-tapping (playing on my phone) like was suggested in another comment, but it didn’t help. The Cancel option is present, but once I click on Buy, I am “locked on” to Buy and cannot switch to Sell or Cancel. I am still able to select any of the various items to potentially purchase. There’s just no option for “okay I’m done buying things now, goodbye”.