When a channel with a LSP is closed suddenly could be because:

• your channel didn't had too much traffic. For a LSP traffic means more fees. All LN channels have an economic incentive to stay alive.
• you had too many times a bad connection and the peer couldn't update the status of the channel. That will trigger a force closure
• you had too many and long period of HTLCs through that channel. Be aware if it was a public channel you can get "spammed" with multiple HTLCs to get closed that channel. Spend more time reviewing your peers and fees policies and also min/max HTLC policies.
• if that channel was private (unannounced) then maybe you had a hold invoice that stayed too much in a pending HTLC and that could trigger also a force closure.
• the LSP also could close the channel anytime or when the leasing period expired, if is not profitable to keep it.

As I always said: running a public routing node is not a joke, you have a lot of responsibility and duties.

Running a private node (non-routing) is another story and you can avoid many of these issues to happen. A private channel is indicating to your peer that you maybe will not be all the time online, so it could soften the policy rules on you. But on the other hand, will know that you will not route too much of other payments, so less fees.