Roland Jupiter 6 freezing when trying to access memory locations

[belzrebuth]

Hi all,
I've got a Jupiter 6 synthesizer that needs some attention.
It had a flat battery so it must have had all of its sounds erased but it seems to be more than this at play here.
I tried restoring the original patches via tape but the process never finishes, this is a quite daunting task with this synth but I don't think this is actually my problem.
When I sent the patch data thru the tape interface all LEDs light up sequentially but the procedure does not end with LEDs A and 1 lit as it should so it might actually be a verification issue.
There is actual patch data on some locations but the synth randomly freezes with I'm trying to access different patches.
Here is a clean copy of the service manual with schematics (page 13 is the digital section):
https://www.florian-anwander.de/roland_jp6/Roland_Jupiter-6_Service.pdf
I'm not sure on where to start with this other than replacing the "tone ram" IC24 and maybe IC18 and IC19 which are responsible for read and write(?)
I'd appreciate some help on what I should look out for..