"Reddit user ZipoTm posted a thread entitled “How I lost 4BTC on the Lightning Network” where he detailed a conversation with support who said the Bitcoin was irretrievable.
“Yes, if you force close using an older invalid state, they can take the money while it’s time locked if their node is online,” they wrote to the aggrieved user.
“Wow… looks like I lost 4BTC because my LND wasn’t synchronised, that’s weird.” ZipoTM replied.
“You have already closed all your channels with an older state? That’s it, the money is gone,” the support reiterated"
https://coinrivet.com/user-loses-four-bitcoin-on-the-lightning-network/