Does anyone know how it effects margin / if you get a margin call if for example you have 100 puts at a strike of $1000 then premarket all of a sudden you have 2000 puts for a strike of $50 and the price firmly below the $1000 strike.
IBKR doesn't do margin calls. It just liquidates positions so I'm worried the way it calculates options and margin freaks the backend systems out and liquifies long term short contracts when they multiply by X (split number) but the strike prices don't update.
If it's IBKR's fault, I'm sure you'll have a case to sue them. With that threat on their shoulder, I highly doubt any broker would mess up the updating of the strike price. They might fail to deliver the shares to you on time (I didn't see my split shares until a few days later), but they won't margin call you due to a mistake on their end.