It sounds like there's definitely something wrong with your MTS services. If/when someone comes out, ask them to kindly check everything and not just swap a box. If they do swap the main PVR, ask if they have a brand new unit with them. Sometimes refurbished units have their own issues, so on repairs I prefer to use new units. I hope you give them a second chance. The service should be rock solid.
You may also want to try the official MTS Community Forum and let them know, and maybe they can look into it more to determine if it's the signal coming from outside or just on the internal MTS network in your home. They have a system that does self-tests and reports any issues not within spec.
Authorized Service Provider (Contractor) for MTS Allstream. Any views expressed are my own.