Tried this solution?

https://support.optimizely.com/hc/en-us/articles/360002481391-Property-PropertySettings-has-unknown-type

In my case I think the correct path is to delete, not update the versionnumbers etc.

I'm seeing three rows returned from this query:

SELECT * FROM tblBigTableReference
WHERE ElementType LIKE '%EPiServer.Editor.TinyMCE.TinyMCESettings%'

Snooping around some more...

SELECT * FROM tblBigTableStoreConfig WHERE StoreName LIKE 'EPiServer.Editor.TinyMCE%'
-- 2 rows

SELECT * FROM tblBigTableStoreInfo WHERE fkStoreId IN (SELECT pkId FROM tblBigTableStoreConfig WHERE StoreName LIKE 'EPiServer.Editor.TinyMCE%')
-- 6 rows

SELECT *
FROM tblSystemBigTable
WHERE StoreName LIKE 'EPiServer.Editor.TinyMCE%'
-- 58793 rows

SELECT *
FROM tblBigTableIdentity
WHERE StoreName LIKE 'EPiServer.Editor.TinyMCE%'
-- 58793 rows

SELECT *
FROM tblBigTableReference
WHERE ElementStoreName LIKE 'EPiServer.Editor.TinyMCE%'
-- 29653 rows