Man United performance looks very unstable lately, it is not really surprising if they missed again 3 points. Ten Hag always changes the starting eleven, which may bring a negative impact on Man United performance. Every time I saw Weghorst plays, Man United probably ends up the match with a bad result. I don't blame Weghorst, but I assume he doesn't fit with Man United tactic.
When you keep on using the same set of player's for every match from the beginning of the season to ending, then the players will get tired, since the beginning of the season till ending Manchester united performance have been nice, but lately Manchester united player's are tired and they need to rest, but they are not getting the rest because Manchester united are not have experienced players in their bench, if we all noticed the way Manchester united players have been playing lately, then we will know something is wrong, I think Ten Hag should just work on getting more players when the transfer window is open, so that he will be able to rotate players in matches.
Personally I will attribute Man Utd unstable performances due to dip in form by almost all the players since Eriksen came back from injury he had been a shadow of former self, Casimero too had been woeful, DeGea too showed his own lapses by gifting West Ham a cheap goal, the likes of Antony, Rashford, Sancho are all playing at a mediocre level Weghorst has minimal input to the team, Bruno Fernandes has lost his creative passes, however I believe Man Utd will still scrape through and take up their chances of UCL qualification despite their dip in form because of their one game advantage over Liverpool probably the team will turn up for their remaining matches.