sound lower one speaker sansui amp,fluctuates,help

[aifrecords]

this is my first time seeting up and playing quad so im just wondering is the following normal? did the seller that sold my old sansui qrx 5500 amp last week stick me with a lemon? this is issue: in phase matrix when playing SQ,the front left speaker is a lot lower volume in ormal direction mode(I have 2 bsr speakers in front ,two infinity speakers in rear.). then i experimented with direction control on amp, i can shift it 90 degreees with every quarter turn. i turned it 1/4 to right, then the speaker that sounded like less volume moved 90 degrees with every 1/4 turn, so in normal mode the less speaker was oroginally the front left,then with a quarter turn to right became the front right,tehn next 1/4 turn to right became back right,etc etc. then i tried qs vinyl and took amp out of phase matrix the sound was then fine and front l speaker in normal direction mode was fine.
the two days later, in phase matrix ,direction normal,front right spkr low volume,every 1/4 turn rotates the lower sound to the next 1/4 turn speaker in that direction. then i put it in 8 track tape and put it into qs synth mode, and in normal mode the front right spkr sounded find and had normal volume. same with a stereo record. so was I stuck with a lemon for an amp? or is this normal? again my 4 speakers arent exactly the same, same brand in front, different brand for rears. and im pretty sure other days when playing sq in phase matrix the speakers sounded even. weird though i put on a stereo dark side of moon master recording vinyl and in qs synth mode same issue in normal direction the front right speaker had less volume.

 

[aifrecords]

the present amp is qrx 5500 that is what i bought last week,old amp from 70s probably.