Following the suggested PIMax<280 and PIFMax<4 guidelines, your Princo scan is not very good, but typical of the poor quality of Princo media. I would be surprised if that disc played without skipping or freezing, particularly at the beginning and end, where the PIFs exceed 4 by a lot.
Your YUDEN000T02 scan looks good, and is typical of scans of this good quality media. The single PIF spikes greater than 4 can be discounted since they occur singularily alone. Those spikes are usually where the recalibration has taken place and the laser has de-, then recoupled from the disc. That disc should play fine on most players. If you are saying the Princo plays fine and the YUDEN skips and freezes, then you have a very finicky player!
Since you are getting scans of expected quality considering the media, what I might guess you are talking about is when you are burning at 8x, your LED occasionally blinks from red(burning) to yellow('buffering', not burning). This is normal for 8x burns and is your drive either shifting speeds or using its recalibration feature, where the laser decouples from the burn for a second or two as the drive recalibrates the power neccessary for a good burn. The laser then recouples with the disc and continues to burn. This action happens several times during a burn. It is normal and nothing to worry about.