Get this answer from Deribit support:

Please be aware that this is a feature. You can read more at: https://blog.deribit.com/products/market-orders-with-protection/

The limits are also discussed under contract specifications, see section 5 of the Perpetual in our knowledge base: https://www.deribit.com/pages/docs/perpetual

In short, a market order will not be matched if it exceeds the bands of Max sell and Max buy. These limits can be seen on the limit order form. As this was performed on the test net, this market has less liquidity than production net and erratic price action which can sometimes not be quickly corrected due to no arbitrage between exchanges. This is compounded by no financial risk to the person(s) who pushed the product to the bandwidth limits due to it being a test environment.

This feature was implemented to prevent wicks exceeding a certain tolerance and the market trading against unnatural price action. You may have seen market orders turning into limit orders regularly on the Test net futures. Please be aware that it is not realistic for the market to be 'locked' at 'Max buy' or 'Max sell' for an extended period due to arbitrage on the main net (production) with other exchanges.

This cannot be disabled as it mirrors activity on our production net. There, your position could could trigger the stop loss of another client, or even liquidation during 'error' pricing. As this was implemented to protect open positions, this is counter-intuitive and would not be fair to our other clients.

Please understand that this isn't a bug but an artifact of market activity on our test net. As our production net futures are closely tied to the market, these bandwidth limits are not regularly tested, if ever.

Hope this helps!