I don't understand why our fanbase thinks Dortmund have behaved badly. From what I gather, they've always said they value Sancho close to £108m, and want the bulk of that payment up-front if any team wants to sign the player. That has been their stand from day-1. Their stand has been clear and consistent. They would have behaved badly if they raised their initial asking price, or if they didn't allow to release the player even if we agreed to meet their price.
Why should they start offering a discount for a player who will probably be valued higher next year and has two more contract-years? And why should they offer any discount to a club that is richer and bigger than theirs?
If anything, we've been penny-pinching and seem confused. If we think Dortmund's valuation is over-the-top, then we should tell them to stfu, and move on to someone else. If we think their valuation is a fair reflection of Sancho's qualities, we should pay up and tell them to stfu, again. It is clear that they won't lower their asking price.
It is nonsensical to suggest that Dortmund have acted badly.