Muddled Center Speaker after Amp Repair?

Hello, wondering if anyone has any insight into what may be going on here.

Just got my Sunfire Cinema Grand amp back after having the capacitors replaced, and suddenly the center channel (ML Theater i) sounds very muddled with severe clipping/peaking at even modest levels. Sounds like dialogue is being spoken through a muffling cloth and in a tunnel. Prior to bringing the amp in for repair the dialogue was extremely clear and sharp as expected for ML electrostatics. Is it possible that an amp repair or cap replacement could affect the sound quality like this?

It's only affecting the center channel, all other speakers have the normal clarity and sharp detailed sound.

Only other issue that I can think might be causing this is when the amp went bad, the power would not even turn on (for the amp), so there was an electrical component to when it went bad prior to the repair -- could it have shorted out the tweeter of some part of the Theater i's range?

About to go back to discuss with the repair shop, but suspect they will deny the repair could have caused this (which may be true for all I know), so trying to get as much info first.

Here's the system:

Sunfire Cinema Grand driving the center channel and the Left/Right front speakers (bi-amping the front left/right speakers)
Martin Logan Theater i center
Front pair: SL3
ML side & rear speakers

Thanks!

Check for malfunction interconnect going from audio video processor center channel output to power amp input. Switch interconnects and see if fault follows interconnect.

To check whether amp center channel is defective replace theatre with rear speaker and connect to power amp center channel. If sound from the rear speaker is also muddled then amp is to blame.

To double check connect theatre to amp driving rear channel speaker and note whether sound is clear and sharp. If sound is clear and sharp then theater okay.

Conclusion:
You need to troubleshoot. This way you can pin point or isolate the factor causing the muddled sound. Some patience and clear thinking may be required to solve this problem.

Good luck! Hope you are able to sort out this issue before thanksgiving. So that you can enjoy relaxing music on thanksgiving.

Great thoughts, thank you -- will do!