Amsin,
Check this blog:
http://www.zerodha.com/z-connect/blog/view/stop-loss-orders-limit-market
This has nothing to do with a bug on the platform, stop loss orders with limit price aren't guaranteed an execution, especially more if the contracts are not very liquid like cardamom.
If you are not seeing an option for SL-M, send an email to
[email protected] and they will enable immediately. Also when you are placing a SL order, in limit price if you mention a 0 it automatically becomes a SL-M order..
What Sl-M does is that when your trigger is hit, the other to buy/sell is sent as a market order guaranteeing u execution..