Maximum number of tripwires I can set

Looking at all the people having the same bug, I think we can say it is a known issue. A player found a workaround though, that corrected that bug for every player who tried it. Here, on PlayStation Community:

I was experiencing the same bug until just recently. I was hit by a corrupted watcher's blinding attack, after the effect ended, all was well again, completely cleared it up, not sure if it had something to do with that, but for those of you who were experiencing problems and the merchant / hunting grounds tricks weren't working, that may clear it up. You can find corrupted watchers in the wild near devil's thirst.

And a comment by another player who got the bug solved:

That did the trick. Although I just went to some regular overwatchers, at the hunting grounds. But yeah, got blinded by one and boom icons came back and can tag again.

I hope it will solve your bug too.

I just checked based on the suggestions in the comments. I can confirm that changing arrow types after nocking multiple arrows will cause the old type of nocked arrows to be unloaded and the new type to have a single arrow loaded. Switching back to the first type of arrow will cause Aloy to only have a single arrow loaded.

However, interestingly enough, unequipping the bow entirely then re-equipping it will result in the same number of arrows being nocked before and after the fact...