Fundamental vulnerabilities you should know about LN.
1.) Network structure - nodes.
Lightning Network nodes are not as flexible as Bitcoin nodes, each LN node requires manual connection setup, each one of them becomes an intermediary, if one intermediary is closed, transactions may not process. That means each node is a single point of failure, especially if it is a well connected node, if it goes offline, a lot of participants will lose the ability to transact with each other, and will require new manual connection setups. Probably that's the reason why some LN transactions fail to process.
2.) Node crash - lost funds.
If you run a LN node, it's not like Bitcoin node, where you can connect and disconnect at will, synchronising with other active nodes. On the lightning network there is no single shared global database. You have to rely on your own data, so if your node for some reason crashes due to HDD problem or operating system issues, you may lose access to your account. That's why you may need to make backups constantly.
3.) Watchtowers - funds can be lost.
If we have such an issue where a network participant can steal funds, that means a critical trust vulnerability, and bringing a trusted third party to watch for your connection transactions is just a reinvention of the old financial system.
4.) Second Layer - a financial instrument whose value derives from the underlying asset.
If it sounds like a derivative, most likely it is. The problem is that when BTC mainnet reaches peak activity it becomes difficult to open and close channels on LN, if this issue raises constantly, removing the peg might make sense.
The requirement to lock BTC and generate Lightning BTC can be modified, or completely removed. The Lightning Network is not built on top of Bitcoin, it's completely seperate Network that can operate independently, even if Bitcoin totally switches off.
5.) Depended on 1 layer, limited scalability.
With limited blocksize on a worldwide scale Bitcoin can be used as a reserve currency for large banks, governments and financial institutions, but can't serve as a payment system for everyday commerce, which leads to second layer solutions necessity, LN is one of the 2L implementation solutions, which is dependent by the first layer. Here is a problem, if we remove the dependence we risk having fractional reserve, supply inflation, if we don't remove the peg, we still can have the same, low risk, but we will be also limited with network scalability.