RE: possible nozzle clog?
Read up on doing cold pulls. The top line looks good until the "squiggly bit" starts. A cold pull will help clear any partial blockage out of the hotend and nozzle easily.
It may be that your Live-Z adjustment also needs to be recalibrated. If you have not already done so, try using Jeff Jordan's "Life Adjust" procedure for calibrating your Live-Z setting. It is much easier to use and understand than the on-board routine. It's much easier to make mid-print adjustments accurately with. In general, start high (less negative) and work lower (more negative) in large increments (e.g. 0.1mm) until the filament starts to stick on its own. When you've got your Live-Z setting adjusted properly, you should be able to gently rub the extruded lines on the PEI surface without dislodging them. Then start lowering (more negative) the level until there are no gaps between layers.
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