SHW160P6S Burn Quality degrading...any suggestions!

All discs are burned @8x and scanned @8x with SB/HT/OHT=on & OS=off
First three discs burned & scanned=2 days back.
Last/Fourth disc burned & scanned=today

These MCC discs are from same spindle. I even tried to reset learn media & HT setting with eeprom utility and then tried to burn few more discs but all discs have same result with lots of PIE/PIF errors. Also i got few coasters today.

Burned different media & got same result high PIE spikes with lots of PIFs

Another fujifilm03 burned & Scanned @ 8x with HT/SB on & OS/OHT disabled

Moser Baer India DVD-R 16X media burned & scanned @ 8x with SB/HT/OHT on & OS disabled. High peaks at the beginning of disc.

Those scans are not all that bad, not great but still good. In my experience, PIEs don’t matter too much, and all of these scans have fairly low PIFs. You might get slightly better burns at 12x, so burn some disks at 12x and if they improve, stick with it, but if not just continue burning at 8x becase all of the disks you have shown should work perfectly.

Moser baer burned @ 12x & scanned @ 8x with pv94 test firmware.
(not as good as 8x burn)

Another burn of MCC02RG20 (not good as before)