I have been using playmemories for last 6 years with Full HD video and it had always worked perfect. With 4k Video, I am using Play memories v 5.4.
Vincent M, if you are part of the 'Play memories' team, I suggest you do some trim test of FDRAX53 4K video (60Mbps/30 fps) ****** with a length of 2 minutes and let us know the result. I did try multiple files and same file few times and result is same. I even tried by frame,...none works. Trimmed file is always off by one (or less) second on both to the begin and end section. All these trimming are doen strcikly on Play Memories with a fast PC.
However I did try some other software and trimming result is perfect as for as end and begin goes, but do not want to use those as they recreates entire file which takes awfully very long time to process and some time add some artifacts as it renders.