Yes same ongoing issue. Either internet throughput drops to below 1mbps (even on a gigabit fibre connection which usually gives in excess of 200mbps when the wifi is working properly on the phone) or says connected but no internet which means it doesn't work at all. In both cases restarting the devices fixes it, usually for around a day before the issue returns. I've tried software restore, factory reset and so on.
To note - Sony don't seem interested in this or at least do not want to comment. Although I know this is a user based forum their support staff (eg. @Jonas) regularly reply to other threads but not once have responded to any of the below threads discussing the same issue:
/t5/Xperia-XZ1-Compact/Wifi-connection-problem/m-p/1315030#M2773
/t5/Xperia-XZ1-Compact/wifi-problem-xz1-compact/m-p/1301712#M2335
/t5/Xperia-XZ1-Compact/XZ1C-and-other-Sony-devices-cannot-connect-to-5-GHz-band-wifi/m-p/1299359#M21...
/t5/Xperia-XZ1-Compact/Ongoing-wifi-issues-even-after-update-to-47-1-a-12-119/m-p/1312798#M2700
/t5/Xperia-XZ1-Compact/Multiple-wifi-sources-connection-issues/m-p/1285840#M1407
/t5/Xperia-XZ1-Compact/5G-wifi-connection-issue/m-p/1263675#M103
At least an acknowledgement would be good that they (Sony) know it is a widespread problem and they are trying to fix - as @PeteCal mentioned in one of his posts, when he spoke to Sony support they didn't even know (or at least the support agent he spoke to) it was an issue.
