MQM tag can not be deleted

STR:
with trackchanges plugin activated
  - open segment for editing
  - add MQM tag

• save segment
• open segment again
• delete MQM tag
• save segment

Expected:
MQM tag should be added in 'ins' tag in editor and remain there after saving. MQM tag should be deletable like any other trackchange with the same behavior (user can delete own insertion completely and in case somebody else's insertion it should be replaced with 'del' tag).

Actual:
Added MQM tag after saving is not in 'ins' tag and not in 'del' tag.