Fatiguing is a natural process as time passes by. I think you've answered your own question when you said that you lose 5 odd kilograms when performing bench after dips. Perform it before and see what happens with that 5kg.
An alternative would be to increase your rest time between exercises to more than what you're currently taking. So if you're jumping straight from one exercise to the next without a break, try a 5 minute break and see what happens.
Fadi.