Application too thick. Apply thick areas of fill in several thin layers. Apply a thinner coat, allowing air to escape easier. Tip off the coating with a roller cover brush to break bubbles. See Out-Gassing caution in the User Manual.
Surface tension causes epoxy film to pull away from pinhole before it gels.
After applying epoxy with 800 Roller Cover, force epoxy into pinholes with a stiff plastic or metal spreader held at a low or nearly flat angle. Re-coat and tip off coating after all pinholes are filled. Fish-eyeing in coating. Contamination of the coating or surface or improper abrasion for the coating. Be sure mixing equipment is clean.