Some leads
Thank you for your email.
There should be a Japanese report after their engineers and specialist reviewed the war booty and infrastructure within weeks of occupying Singapore in 1942. The most famous of these is the fortress fact finding team led by Lt.Col. Masataka Numaguchi of Army Technical HQ and Major Katsuji Akiyama of the Army Heavy Artillery School which produced the original Japanese Monograph No.68 (published by the Chief of Military History in 1958). I believe there must be similar files evaluated by the Japanese Naval Board for the the Singapore harbour and docks where the cranes were purportedly to be last seen.
Apologies that I cannot be of further help, I wish I know which precise direction to point you to, but the Public Record Office, and the National Library of Australia holds copies of the above Monograph No.68 and I believe other files pertaining to the after the battle survey/inspection carried out by the Japanese.
I hope this helps somewhat.
Regards,
Chen.