Fish scale pattern on catheter

Hi all, I am having issues when reflowing a catheter using a 40D resin pebax segment. It is presenting a fish scale effect defect, these are little flashes in a regular pattern. Materials are PTFE internal layer, PET braid middle layer
and 40D pebax on the outer layer. Material is being reflowed using FEP as heatshrink and a single chamber single temperature reflow oven.
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