Villagers have no trouble connecting to beds, as they can pathfind there without any problem. However, they "forget" them sometimes upon wandering around the village, and connect to other unclaimed beds in the village boundaries, leaving their previous beds unclaimed and up for grabs. This should not happen. 

I suspect that the cause of the issue is the distance between the villager's bed and a gathering site, as they leave their beds and have to walk some distance to gossip with other villagers. Upon being done they do not return to their own beds but seek closer ones in the area, due to either wandering even further from their beds, as it is part of their daily schedule, or some other unknown issue.

This is a minor issue in the game, but unintentional nonetheless. It also causes issues around building a village by yourself, as villagers do not use their houses as intended.

This could be fixed by completely removing the ability from villagers to seek other beds if they have claimed a bed no matter how far it may be, and only have them reset their beds by breaking the ones they have claimed.