@sponch could you try the following:
create an app backup
switch Recovery Mode on
copy /app/data/data/installed_plugins.json to /app/data/data/installed_plugins.json.bkp
update plugins versions by amending /app/data/data/installed_plugins.json as:
{"plugins":[{"name":"ep_align","version":"10.0.2"},{"name":"ep_comments_page","version":"10.0.4"},{"name":"ep_embedded_hyperlinks2","version":"1.2.4"},{"name":"ep_font_color","version":"0.0.89"},{"name":"ep_headings2","version":"0.2.68"},{"name":"ep_markdown","version":"10.0.1"},{"name":"ep_openid_connect","version":"3.0.13"},{"name":"ep_user_displayname","version":"1.0.7"},{"name":"ep_stable_authorid","version":"1.0.5"},{"name":"ep_guest","version":"1.0.37"},{"name":"ep_etherpad-lite","version":"2.2.6"}]}
delete /run/etherpad-lite
switch Recovery Mode off
If the app doesn't get running, please post the app log.