Is the Ctrader platform automatically rejected this order which have a negative slippage

Dear Ctrader Team,

Could you explain for me the Ctrader platform have this function? and if the Ctrader platform automatic reject the order what is conditions for this rejection?
Recently, My order have been rejected and the broker explain that Ctrader will automatically rejected any order which have  a negative slippage. For example: I have Buy limit order with my request price to create order lower than the next available price . It will be rejected.
10/07/2019 09:05:53.284 | → Request to Buy NZD 23k NZDUSD (Price: 0.65688, MR: 5) is ACCEPTED, order OID56133621 created (10/07/2019 02:05:53.078 UTC+0)
10/07/2019 09:05:54.613 | → Order OID56133621 is REJECTED with error ""

Thanks and best regards

Cong Truong