I'm glad that you were able to resolve your issue! I'll repost your solution in case you'd like to "Accept " the answer.
Issue:
You were unable to write or edit permissions for your disk. The disk was showing mounted as read/write, but still root could not make changes.
Solution:
The directory was set to immutable. You discovered this by running:
root@vm:/# lsattr -d /models
----i---------e------- /models
Running chattr -i and chmod you were able to resolve this.
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