I guess I found a solution. I'm not quite sure it's perfect, but it works.
Replace in getWhoViewReadStatsWRT and getWhoViewReadListWRT methods:
->where('params', '=', 'thread_id='.$this->thread_id)
With:
->whereOr(
['params', '=', 'thread_id='.$this->thread_id],
['params', 'LIKE'...