what would be the reason why Resolume would render too fast which would result in having to hold a frame for an extra cycle and skip one cycle for the next one?
Any of one thousand different processes starting and stopping each render cycle. Remember that we're talking about the predicted time that the render cycle will complete, and which frame should be visible at that time.
would there be a way to offer an option to switch between seek and push modes at the clip level
That would be one obvious solution, yes.
Unfortunately this gives all sorts of unexpected behaviour, since it involves handing complete control to the playback engine, and thereby we're forced to bypass other steps in the pipeline. For instance, audio playback will use the system settings, rather than Resolume's settings. This means that by changing a clip to this playback mode, all of a sudden your audio will be routed to the system default and completely ignore the volume and master faders in Resolume.