Similar to bug #183, when manually stacking a decoder on top of another one, the full list of potential decoders can get very large and there's no scrollbar or similar mechanism to handle this.
Fixed in cf0a3c9c7a8763eeb4427e4fb6fe2c921ae38f09 by reducing the number of PDs to just those that can actually be usefully stacked on top the of current one, thanks!. An additional fix in 15784350767c05f3afb2f9af0c4b212a89493e30 makes the list scrollable as well.