I’ve never come across this problem. But here’s a workaround until someone comes up with what the source problem is.
Place .psd 2 on layer above .psd 1. Have .psd 2 overlaps .psd 1 by however many frames you want the dissolve to be.
Right click .psd 2, select open in viewer. Now go to the motion tab, and set keyframes under the opacity option to have the file fade in over the duration of the the dissolve.