HELIX APP on FIRE TV has problems when ISP for TV is changed

Because Videotron is my ISP where I live in Kirkland, I am allowed to use their HELIX app on my mobile and non-mobile devices when I am away from my home. Up until a week ago, I could use the HELIX app on my iPad and iPhone when I was visiting my family member who lives near Valleyfield in spite of the family member not being a Videotron customer. The HELIX app was also working on a Windows PC and a FIRE TV at the same location near Valleyfield using my own HELIX account. A week ago, the family member's ISP (Groupe-Acces Communication/Centre Tess) suddenly closed their business and she was forced to subscribe to a new ISP (Targo), who quickly installed a new fibre optic service with a new modem/router. After this installation, the HELIX app continued to work perfectly on all our devices except on the family member’s FIRE TV. 

The moment any navigation button was pressed on the TV's remote, the HELIX app took exactly 150 seconds to complete the request. I consulted with GOOGLE AI who suggested that I try connecting the TV to the Videotron HELIX servers using the wi-fi hotspot connection of my iPhone. Doing so corrected the problem, so GOOGLE was satisfied that neither the TV nor its HELIX app was corrupted. I told GOOGLE that the Targo supplied router was making IPv6 available to the TV along with IPv4, and GOOGLE suggested that our 5 year old Toshiba FIRE TV might not have been designed to handle IPv6 efficiently and was taking 150 seconds before defaulting to IPv4. GOOGLE suggested that I ask Targo to remotely turn off IPv6 on our router, which they did, but this did not help.

Yesterday, I connected (cascaded) the old router, that previously allowed the FIRE TV to successfully operate the HELIX app with our former ISP, to the new Targo router using a WAN to LAN Ethernet cable. That solved the problem and allowed the HELIX app to run properly on the FIRE TV.

Today, I turned off the old router's wireless network so that there would only be one wireless network in the house and the only device that would use the old router would be the FIRE TV. I should point out that we always connect the FIRE TV to its router using an Ethernet cable.

I believe that this workaround succeeds because the old TP-LINK router (circa 2012) has a firmware design that allows the communication from the FIRE TV's HELIX app to travel successfully between Targo and Videotron servers, whereas the modern Targo fibre optic router (also TP-LINK), doesn't. There is also the chance that 5 years ago, I tinkered with the old router to force it to route via the Google’s public DNS server (8.8.8.8/8.8.4.4). Apparently going via the GOOGLE DNS cuts Targo out of the loop, so any incompatibilities between Targo and Videotron are no longer an issue. It remains a mystery to me as to whether it was Targo or Videotron who was waiting 150 second before issuing a timeout error.

So if you are running HELIX on a FIRE TV that resides in a remote residence not connected to VIDEOTRON and the home owner there is forced to subscribe to a different ISP, don’t throw away the old router.