The ETH, which the user sends in the likeUser function is not accounted for in userBalance. This means that the ETH will be forever stuck in the protocol and not sent to the MultiSig of the users who had a match.
High as it defeats the core purpose of the contract and causes loss of funds.
Manual review
Add this line of code after the checks in the likeUser function:
Likelihood: High, always. Impact: High, loss of funds
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