I'll give you an "unofficial" official response to the question.
Yes: 1.53 is bugged and the tsumuxer doesnt work most times and
yes: 1.53 sometimes files can not be found.
What I do in these cases is of course download mkv2v0b 2.4.7, (the newer ones are bugged bad and there is no longer any support for over two years) use that to make them into m2ts files and transfer them with a flash drive.
But fear not! The fix to this will be close behind if I know these folk.
PS: Has anyone noticed that the file hesitation has gone away since the last Sony update?