Katja took a some damage fighting the guards and used a few stimpaks, so I was trying to re-stock her supply after the battle and I couldn't give her a weightless stimpak. I too also first noticed it at the military base. Since Katja has such a low carrying capacity, I use her to carry spare ammo for me and items that I use but don't need taking up space in my inventory like doctors bags, med kits, lock picks, etc, so I'm rarely giving her items. I'm using the unofficial 1.3.5 patch, so maybe it fixes Ian and Tycho. This was driving me crazy, but unlike the OP, it was only happening with Katja.

I know you can give unlimited items to companions through barter, but I feel that is cheating and don't use it. If you take off the power armor, you'll be able to plant items again with the steal skill. I found the problem and the solution on my own, so I'm posting it here for anyone in the future that runs into this problem and looks for a solution. Sorry to resurrect this almost 9 year old post, but I was having the same problem and this was the only relevant hit I found when searching for a solution. This happens with all NPCs at some point near the end of the game and I am trying to figure out exactly what causes it. I can use steal and take everything away from him, but when I try to plant anything at all, even returning items I just stole, it tells me 'there is no more room for that item.' Sometime after I have entered Cathedral or received the quest to find the Military Base this changes. We sell the scorpion tails and I can plant something else on him instead. During battle he uses the shells and stimpacks, so I plant more on him. I always used steal and plant to exchange items with NPCs as that was what I read to do somewhere, but I don't see how using barter could make any difference in carry weight.ДЇor example: imagine if Tycho can hold 1 shotgun, 10 shells, 5 scorpion tails and 3 stimpacks when we leave Junktown. What I am saying is that it changes at some point during the game. Whether or not the carry weight is determined by size or volume is not the problem here.

I guess I am not explaining this properly. I just thought that with a 10 year old game, someone must know about this already and I wouldn't need to do that. I'll probably start a new game (or an older save) and check after entering any new area beyond the Hub.

I'm trying to figure out when/what triggers this. In older saved games the NPCs still carry things as normal so I think it's part of the way the game timeline is designed. I tried restarting several times and it does the same thing. This happens late in the game and I had visited the first part of Cathedral and then back to the Military Base. So I don't think it is the weight.ДЄt first I had to take away the throwing knives from Katja to give her a SMG and ammo, but then when she ran out of ammo I couldn't give any more. I even tried taking away ammo they were carrying and then they would not take it back. That was when I discovered that they suddenly couldn't carry anything more. I sold all the items then went hunting mutants for more things to sell. I loaded them up with twice as much as my player could carry. Both Ian and Tycho could carry much more than just weapons and ammo though.

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