After reecent updates (probably 2.1) putting silent legion armor in delving bench won’t give you chieftain armor recipe. Tested with 200 armor pieces on single player.
Please provide a step-by-step process of how the bug can be reproduced. The more details you provide us with the easier it will be for us to find and fix the bug:
1.put armor pieces in delving bench
2.waste time and resources