There’s a lot to say about it, and also a lot that has already been said. If applied properly, the SkyConnect dongle is as good as any. And the problems you have might also happen with another hub if you stumble into the same pitfalls.
There’s a whole section of good posts here:
The most common pitfalls are:
Failing to use a proper extension cable to get away from interference
Failing to pick a proper channel, away from interference
Not having enough zigbee router devices
Cutting power to zigbee devices that act as router
Pairing devices in another location then where they are used
Majority of the issues like this are due to lack of enough routing devices to make the mesh stronger and allow more overall connections back to the co-ordinator.
Yes it can if you use the multipan firmware to run both at the same time else its one or the other, and currently its best to have a dedicated one for each until more work is put in with the current issues with the multipan firmware.