Weird issue of volume up/down automatically

[prash2k01]

Recently I got a six month old focal solid 4 amp for my from a friend for my Ritz car.
before that I had JBL amp which was working fine and was installed with local/cheap cables without any issues.

but after the focal installed in my car...I found the big difference in SQ.
I have focal polyglass comps in front doors and JBL co ax in the rear doors.

Issue:From the very next day from focal amp installation I found that volume automatically goes up/down without any change
When occurs: there is no exact instance for this issue
It goes down with a/c switch off and some time it goes up when speed comes down

Steps: I called the focal Mumbai dealer, he said it is issue with power cord than I changed the power cord with finolex power cable 15mm which is
3 times thicker than the local one
Also I have changed the RCA from MX RCA cable with gold plated plugs
Speaker cables are also good one
Impact of change:
There was a big change in SQ but the volume issue remains the same

Expected help here:
What to do to resolve this weird issue of volume up/down automatically

Questions:
Is this issue with cables?
Power from battery?
Or
With amp?

TIA

 

[prash2k01]

experts plz help

 

[prash2k01]

Dealer says it is issue with head unit grounding.
An expert says it is with rf chip

Don't know what to do?

 

[prash2k01]

Issue resolved closing the thread

 

[nikhilstomer]

What was the exact issue?

 

[prash2k01]

Issue was volume go down by 50%