Let me make a comment or two:
Without having a permanent reservoir - whether that be the internal one created by a solid bottom and holes in the side, or an external one created by the pot (with bottom perforations) standing in a tray of water - that is not semi-hydroponic culture, but is just "traditional" culture utilizing inert media.
The death and subsequent loss of roots to rot is to be expected. Root cells tailor themselves to the environment into which they grow, and once grown, cannot change. Moving roots to a different environment makes them less than optimal, so the plant will have to replace them, leaving it vulnerable while it grows a sufficient new root system. That is why it is important to move plants to a new root zone environment right as they are beginning to grow new roots - a short gap won't exhaust the plant or be sufficient time for desiccation, but if the plant is not actively growing new roots, it is possible to lose it before it can.
Another thing to consider - expecially with "hot growing" plants like phals - is that the enhanced evaporation of an open, airy medium like those typically used for S/H culture, can lead to evaporative cooling of the root system (if the rest of your growing conditions favor it), potentially pushing the root zone temperature low enough to weaken the roots, leaving them more susceptible to attack by pathogens.