This is what Bobble posted on patreon yesterday:
"Firstly, I must still stress that a deal is still there to be had, with Tyler Dibling wanting the move and Southampton being open to selling at the right price. Will Still integrated the 19 year old back into training late this week and the winger has since featured for Southampton during their 1-1 draw against Ipswich Town on Sunday (coming on as a substitute for around 10 minutes). Further talks are planned over the coming days, with Southampton's patience wearing thin and wanting a conclusion one way or the other. The sticking point remains the structure of the deal. Southampton are demanding an approximate £40 million guaranteed (with an agreement almost settled for this) plus add-ons and clauses, which would take the overall deal closer to the £50 million mark. Ultimately, add-ons and clauses are only useful if they are actually achievable. For example, Southampton could demand a £10 million clause if Everton win the Champions League - unfortunately that's not likely any-time soon. However, on this occasion the clauses and add-ons still demanded from Southampton were almost certainties rather than debatable, meaning the deal is effectively around the £50 million mark. This was a valuation Everton felt was too high. Once again, more talks are planned between the two clubs, with the players camp still hopeful that a deal can be struck. I fully appreciate both clubs' stance but the terms of the deal are not far apart (in the grand scheme of things) and I believe if Everton really see Dibling as a future star, this is a deal that needs pushing over the line."
Sounds like its the add ons that are the sticking point.