The price exceeds strike-difference error occurs when you attempt to close a credit spread position with a price that is greater than the spread’s width.
For example, this “Demo Live Bot” has a $1 wide call spread. The position cost $0.29 to enter.

If you enter a $1.05 limit order, which is more than the spread’s width of $1.00, you will receive an error message.

The close position order is rejected by the broker because credit spreads cannot exceed the strike difference.

The position remains active in the account after the error is received.
This failsafe is in place to protect you from overpaying and taking a larger loss than necessary on a spread position.
SmartPricing avoids this issue. This error will only occur if SmarPricing is turned off and you try to manually close a position for a price larger than the spread’s width.