The best solution might be to make a copy / backup of your project, then upgrade to 5.3 to see if everything else runs fine as well, then stay at 5.3. Downgrading a project is not supported.
Because so many things change per version it is common that a newer version fixes one thing while breaking another. Reporting a bug on an older version has little use since it works fine on 5.3. EPIC does not look back to older versions. If EPIC would release an LTS version of the engine (long term support), we could stay on the same version for much longer and request fixes for that version: