I have two alts that are bugged on the Trial of Execution. Zatty and Bronc both have killed the Executioner, but cannot enter Plane of Valor. They did the hailing of Mavuin, killed the waves and the Prime Executioner, but when they provided the "evidence of Mavuin" there was no response and hailing Mavuin again also gives no response.
The issue I believe .. they were in a raid when they had their wins. I have done it again without the raid but have the same results.