Yes, Spine major versions (3.6, 3.7, 3.8, etc.) are not compatible with each other. The Spine Editor version you export from must always match the Spine Runtimes version. That exports from Spine Editor 3.6 (mostly) worked with Spine Runtimes 3.7 was merely a coincidence. More info here:
Settings - Spine User Guide: Version
Spine editor and runtime version management
You can use the Spine CLI to convert Spine 3.7 projects to Spine 3.8 projects. See
Export - Spine User Guide: Command line
