"back up" where you are drilling holes, with a scrap coupler....wooden dowel....PVC pipe.
Any thing that will keep some pressure just below/inside, where bit comes through.
Use high speed bits and drill "slowly" through the tube.
The issue is with all the new spiral wound tubing. It "pre-stresses'' the tube during the winding process on mandrel, any cut...hole...slot, etc. want to splinter as winding pressure is released as the bit comes through to other side of hole.
Older convolute wound fiberglass tubes [where glass cloth is wrapped around a mandrel ] never did that.