Geometry fails to trim

seemingly simple geometry of a long closed cylinder fails to trim, split, boolean (when extruded)

Intersection returns a closed curve which still fails to trim, split, boolean (when extruded)

fail_split.3dm (566.4 KB)

Hello- for some reason the edge and vertex tolerances on the cylinder are way out of whack (What command) - Explode, RebuildEdges Join and then trim.
How was the cylinder made/edited?

-Pascal

Thank you Pascal! Worked out.

The cylinder was part of block which was exploded. The block was placed along a curve via grasshopper and Elefront