Make sure it is not too close! if so you will potentially be operating in the near vs far field and also with risk of overloading front end etc. Make sure node is >>3m from test TTIG or add some intervening absorbant materials (simply placing on oposite side of an internal wall usually does the trick 
). The other GW in the property will be operating ‘normally’ with device some distance away.
I tend to run my TTIGs with external PSU or battery powerbanks rather than using the build in main connection as this reduces device level power and local thermal issues - also allows better placement away for usual power socket positions, without having to run bulkier mains extension leads. Should work fine as within design tolerances even f hotter on internal power but I find better with external power brought in over USB feed - also eliminates a small amount of local potential RFi from in built PSU.
If TTIG has been offline/disconnected its websockets connection with the server due to time out then uplinks inc Join Req’s may get ‘missed’ until websockets connection reinitialised and established. If you run several local nodes then the TTIG has greater chance of ‘staying live’ due to reguar traffic and being connected when needed.