The chief scientist of Bitcoin Unlimited, Peter R. Rizun, has recently affirmed that the Bitcoin Lightning Network users may lose all their money while transacting on the network and that it will not be their fault.
Rizun is not fan of the LN, that much is certain. According to him, the Bitcoin Lightning Network has issues. Most of these issues are that it has bugs and also dynamic fees which can increase unexpectedly. For instance, he has affirmed that the users could lose their money because of the L1 fees.
Due to block size limit (something that Bitcoin Unlimited is trying to increase), the fees are high and too volatile if there is a lot of demand. The Lightning Network was mostly created to make small and quick transactions, but its use is increasing recently and the fees are bound to increase with it.
The price of the fees is often discussed in crypto circles and the general consensus is that it is needed, since miners want their money, but that it is often too high. It looks like the LN continues this legacy problem from Bitcoin Core.
This is the explanation used by Peter R. Rizun was that fees spike too quickly. If you have, for instance, $50 USD and the fees rise to $10 USD, you will have only $5 if you make literally two transactions. Your channel partners may also be concerned that you will not have enough balance to cover the fees, so they will close the channel when you do not have any money.
Recently, the Bitcoin LN is growing a lot. The capacity of the network is ever increasing and the bugs are being ironed out, so it can be said that the LN is having a great tme right now. Bitcoin Unlimited was the first initiative to raise the size of BTC blocks (before even Bitcoin Cash existed), so it is normal that the criticism will happen.
The whole Bitcoin Core network (including the Lightning Network) is a competitor to Bitcoin Unlimited, a project which is not as popular anymore, so it is expected that we will see this kind of claim now. This, however, does not mean that the criticism is not sincere and that Rizun is only promoting his own project. Luckily, we have several options to choose from.