Log stash parsing invalid json string issue

I am facing issue in logstash 7.6.1 while reading a mesages which is json but nested map is in json string which cause it invalid json and logstash gives json parsing error.
I tried to remove that tag from message but its faile.

[ERROR][logstash.codecs.json ][voucher_data] JSON parse error, original data now in message field {:error=>#<LogStash::Json::ParserError: Unexpected character ('c' (code 99)): was expecting comma to separate Object entries
at [Source: (String)"{ "transactionNumber":"20241112191234527010000001514", "version":"1", "eventType":"Report", "timestamp":"2024-11-12 19:12:35", "comments":"{"mode":"off"}", "resultMsg":"SUCCESS", "user":"awais",[truncated 613 chars]; line: 1, column: 205]>

someone could help in it