MK2 Heatbed has random struggles getting past 90 degrees?

Hello all! Newbie here. I am having an issue where about 50% of the time my heatbed will soft cap its temperature at about 92 degrees. I would like to get it to 100 degrees consistently to print with ABS, but ill get one print in, and then It'll cool off a bit, and then it is a downward spiral as it slowly cools to 90-92 degrees where it will refuse to get warmer (I've waited upwards of 30 mins, and nada).

Based on other threads that have similar problems to mine, It seems like it might be underpowered, but why is it only occasionally that it does this?
If you could point me in a starting direction, It would be much appreciated. Thanks!

Check the voltage on the heated bed, should be 12v

Also your polyfuse might be over heating and cutting out. Putting a fan on this will stop the polyfuse from getting so hot and tripping.

For ABS I use Buildtak at 65c with no issues.
I also partially enclose the printer using 3 sides of a cardboard box.

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