There’s a lot of misinformation circulating in social media. Unfortunately, very few people care about doing basic research to find the facts.
From FT:
The big brokers who do their own clearing (members of the DTCC clearinghouse) had to immediately deposit additional collateral because of the increased volatility of GameStop and AMC.
Many of them, including our execution intermediary, which is one of the biggest brokers in the world, had to stop accepting BUY orders for these stocks for 1 day because it takes a little time to transfer billions of USD.
As soon as the additional collateral was deposited, trading was restored and on Friday our clients were able to trade GME and AMC without limits.