Unpopular opinion: My old boss was right about cheap thermal paste
He told me to always spend the extra $3 on Arctic Silver 5, but I used a generic brand on a gaming PC repair last week. The CPU temps spiked to 95C under load and I had to redo the whole job.
But is it really the paste? Could be a bad mount or not enough pressure from the cooler. Seen plenty of cheap paste work just fine if you apply it right.