I am not sure whether this will help, as for me this happened using a self host collabora server. If you have access to server/proxy that is running collabora then it might.
I think the reason might be that nextcloud decided to use larger chunks when uploading documents to Collabora then before. My server was setting behind an nginx proxy with the default setting of lient_max_body_size. When I did use a setting of 512MB it worked again.
Now my nginx config has
# set max upload size and increase upload timeout:
client_max_body_size 512M;
client_body_timeout 300s;
If that is not possible for you then you might to search how to change the chunk size that nextcloud uses when uploading to collabora.