[BirdWatcher]

Considering that defensive efficiency is a measure of the proportion of balls put in play in their zone that are turned into outs, it needs to be remembered that for catchers this is mostly popups and squibbers or bunts in front of the plate.
While catcher defense is crucial this measure is a very small part of what a catcher does defensively and given the sample size in your question the total chances we are talking about is going to be small enough that those 4 errors can have inordinate impact on the stat.

It should be noted (as I understand it anyway) that Catcher Ability is a rating that incorporates a number of things, including error propensity, for a catcher. That infield error rating you referred to only comes into play if you play that particular player at first base, second base, third base, or shortstop. (And, of course, if you did play him at one of these positions- assuming he had skills enough to play that position and got some experience- he would commit a high number of errors. That is what a low infield error rating means. Think of error ratings as actually being ability to avoid committing an error ratings.)

Sounds like he muffed a few plays and given the rather small number of total chances we are talking about it has led to a low defensive efficiency statistic. I wouldn't worry about it. No doubt in many other more important ways and as measured by other statistical tools he is helping your team.

Edit: I should probably have added that this particular statistic is far more useful as a team measurement than as an individual player measurement. And while I can't be sure of this, I suspect it is even less useful as a way of measuring catcher defense than for almost any other position.