It's a big WHY.

If you are 100% sure it is not your phone that interrupts the remote, check your router, network, firewall on PC, etc.

It can become very complicated if your house has multiple levels network setup with various intermediate network devices hosting the connections.

I think a small remote app connection should not work very aggressively for any connection drops and retrying.
It could be annoying on PC side as the app doesn't have to do any real-time video or multimedia streaming.

Quote It's a big WHY.

If you are 100% sure it is not your phone that interrupts the remote, check your router, network, firewall on PC, etc.

It can become very complicated if your house has multiple levels network setup with various intermediate network devices hosting the connections.

I think a small remote app connection should not work very aggressively for any connection drops and retrying.
It could be annoying on PC side as the app doesn't have to do any real-time video or multimedia streaming.

Router is configured exactly the same as it was working a week ago. Nothing has changed. Network hasn't changed, still connected both to the same wifi, even tried a different router, firewalls are all set to allow traffic through, disabling firewall didn't do anything, wifi card power automatic disabling was turned off but nothing changed, reinstalled PowerDVD and the remote app
AND
nothing. Absolutely nothing changed. Either I can't connect or if I do, it still disconnects.

Not to worry though, I've found a workaround. A wireless USB mouse. Far more reliable and does the job without any connection fuss. Or as a backup to that, I can use Teamviewer. With no fuss.

Appreciate the lack of help though!