Partial coverage is broken in a C project

[bqqbarbhg]

Describe the bug

I've been using Codecov to test ufbx for years and it has been quite stable so far.

A few days ago my partial coverage fully disappeared in all new uploads, see this example PR, which does not change any code related to coverage.

@@               Coverage Diff               @@
##           integration     #156      +/-   ##
===============================================
+ Coverage        95.41%   99.14%   +3.73%     
===============================================
  Files                2        2              
  Lines            17081    17081              
  Branches          5339     5339              
===============================================
+ Hits             16297    16935     +638     
  Misses             146      146              
+ Partials           638        0     -638     

Environment (please complete the following information):

Partial coverage is missing both in GitHub comments and in the Codecov website.

The coverage is uploaded from GitHub actions via https://codecov.io/bash, as the upload action is broken in self-hosted runners for some reason.
There is an extra -y flag passed to the script, but it does detect the correct codecov.yml anyways.
I have fixed that in another PR, where the issue reproduces as well (but in this one there are a lot of content changes as well).

To Reproduce

• codecov.yml
• Uploaded via bash <(curl -s https://codecov.io/bash) -F tests -f coverage.lcov.

Expected behavior

Partially covered lines are retained in uploaded coverage, as they have been a few days ago.