mac mini – sharing files from Mac (ubuntu os) to other mac machines

I am trying to set up a file sharing server with an old model mac mini that is running ubuntu 20.04. I am trying to share office documents from the mac mini (server) between other client mac machines.

i am having a frequent issue where the client machines are not able to open new office (word, excel etc) documents between each other.

i keep getting these frequent errors on the mac clients ‘this file is locked for editing’ and ‘This document “x” could not be opened’. Has anyone encountered this error and/or have a solution?

all other files open fine, it is just Microsoft office documents that are giving this issue, im assuming its an office problem but if anyone could supply any info i would be very grateful.

Thank you

(apologies if i haven’t been specific enough i am very tired and have been trying to solve this problem for almost a week now please let me know if any more info is needed)