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

After a family member's ISP switched to Targo, the HELIX app on a Fire TV became unusably slow, a problem that wasn't present fmc4me on other devices or when using an iPhone hotspot. The user's successful workaround involved cascading an old router from the previous ISP to the new Targo modem/router, which immediately solved the issue. This suggests the problem lies with a routing or DNS incompatibility between the new Targo network and the Videotron servers, which the old router's firmware or its specific DNS configuration successfully bypasses.