I had a Plus 8 and it was a known quirk. When mine developed a squeal I took the belt off, cleaned all the pulleys and wiped the belt ( it was nearly new and good condition) clean. Replaced and tensioned. No squeals for 10 years! This was the simple first tion. A second option on Plus 8’s was fitting a slightly narrower belt ( see gomog).
Try the tension/cleaning options first before checking pulley alignments.
The KISS principle. I had a poster on my office wall....
Keep
It
Simple
Stupid
!
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