"First time I have run into tolerance issues on my Prusa" Topic

So in my thread on Buildings as gaming pieces I cover a card and 3DP hybrid structure. The 3DP part was a push on structure to stop the fold flat internal structure from collapeinh when in use.

Now this did require high tolerance slots 0,3mm (12 Thou) and 0,6mm (24 thou) slots. All went superebly well everything fitted perfectly on the prototype and appeard to work on the remaining 5 pieces built at the same time using the same file.

However I hit a problem one of the 5 I could not get to fit. In the end I assumed there must have been a fault in the slots of this item but that did not appear to be the case. Finally in a desparate attempt to understan the issue I looked closely and could convince my self it was perhaps a bit small on the slots. Remember its hard, as the slots are very narrow and a diffrence of even 0,05mm (2 thou could be critical). I picked another item and it fit perfectly. The conclusion, either due to slicing variation or just very small devations of the priter head positioning and I had got a tolerance issue. Has anybody had a similar issue and have they found a reliable workround?