Syntax module not highlighting correctly

[Sinsho]

The syntax module for highlighting in quill does not work as expected. It wrongly highlights code (in this example json code).

Steps for Reproduction

1. Visit: https://quilljs.com/playground/snow#codeN4Ig9AlgdgJgpgDwHQCsDOIBcIDGB7KNAFwAIBHAVwgBtqSBeEqOAdxIEUraAKAcgGI4MCETwAnXgBoSwADpQSJALZ4YFanDSYZ8xYrQBPKEQCGCbXIV7FAC2rptLaDDwskd9JN3WS1E1ABzChMAzW0AbW8fGRIAazgDbVkQdAJk6T8AIzhqJJS0NJASAF8ovQBdLytFYqrrUTxqTJMxCLLFcN58eABaTOo8HFjeSrLRq1rvIhs4JThtXjQoVykSMDAScRJeTIpM-rheeWKASgBueUoaaiQAM3ElEyI+brg+gaHV3lSoL4o0OASc6XLg3aAAsREAAqiGeAAZpLw5N5kv40CxAWhkm0QABZPAUYwkACiADdAZoiOkSMkACIUe4UMRoAAOIgAXnBqckAAo0J7-ZLlWTHXjnECScDORDuIhKahYEAAHmEpJIEBg9GSQhE4mSAD4lWBVfr5PIlWgcGIICzSGgxDgtVLYDL0AajZbrbb9SBikA

Expected behavior:
Correct highlighting like this:

Actual behavior:
The punctuation ":" gets annotated as the attribute, the string "Mount Everest" gets annotated as punctuation and all the following "," (except the first one) as well as the closing "]" get annotated as string.

Version:
2.0.2

I have tried to find out where the bug comes from in the syntax module and have found out following:
The Delta object as well as the container returned in highlightBlot on this line contain the correct annotation. These are the children returned as the container:

I have failed to find out where it exactly goes wrong (the time between returning the correct delta and actual modifying the delta to some incorrect state) and would be extremely happy if somebody could take a look at this :).