NextCloudPi shows bigger files as max. 1.1GB

hello guys,
we are running nextcloud 15.0.7 on a raspberry 3b+ via nextcloudpi image 1.12.7.
the datastore is connected over cifs to a nas. so far so good.
but as we would like to download bigger files, we are facing the following issue:
for example we would like to download a zip which is about 5GB big, the webinterface only shows 1.1GB. if we download it actually the download stops at 1.1GB as expected. but the real file on the nas is still about 5GB big.
we didn’t change anything in the config, its running (except for the necessary changes) like a new image.

does anybody have an idea ?

thanks for your time, i appreciate it!
best regards, alex

try app flowupload for big files…