Help Taiwan and Philippine rebuilt ties by demanding The Philippine authority to conduct joint investigation with Taiwan

This is pertaining to the killing of an unarmed Taiwanese fisherman by Philippine coastsguard at the overlapping exclusive economic zone of Philippine and Taiwan. The Philippine authority had previously promised a joint investigation with the Taiwanese authority. Which the government 'welcome the Philippine Government’s pledge to conduct a thorough and expeditious investigation into the incident and cooperate promptly and fully with Taiwan investigators.'
Yet, when Taiwan investigation team arrived in the Philippine on 16th of may, they were denied access into the investigation matters.
Hence I hope to urge the Government to adopt firm stand to pressure Philippine authority to conduct joint investigation and released relevant footage for clarification so to ease tension btw the 2 US ally