The only thing I can think of is debris. Popping up from under the table. I would take the blade out, give everything a good wipe down. Install a new blade, blame elves.
Does your blade slip or lose tension?. Does your tension lever release for no apparent reason? I was wishing I never bought my EXCALIBUR. The upgrade fixed it.
For what I spent it was worth it.
I never figured it out. I used the knob in the back. Wrong, I know, gave up caring. I bought the Pegas upgrade, all problems are solved. Including blade slippage
I had s Scroll saw class last month and one person brought a Delta. We checked it out beside the Dewalt. It appears to be the same Saw with a different color on it.