I have found a temporary workaround for this issue.
Navigate to your 'ForgeVersion.json' which you can find under %userprofile%\.gradle\caches\minecraft\ (Windows)
In this file you need to replace a "0" underneath whichever version of Minecraft your mod uses, with the correct forge release version.
For example I am using MC 1.12.2-14.23.5.2814, so I end up with:
"1.12.2": [
14.23.5.2814,
0,
...
You can find out which version your mod needs in the build.gradle file.
Once you have done this set the ForgeVersion.json to read only, to prevent the update from overwriting your changes.
However, make sure you remeber to remove the read only property when this issue is fixed!