For the past few months I've been having considerable trouble with what appeared to be focus problems. If you are sure of your coating technique, I would begin viewing each new grid by spreading the electron beam just wider than the length of the grid slot and irradiate the whole thing for about 10-15 minutes prior to taking a closer look. If this still is not enough I would consider making thicker films by increasing the concentration of your formvar solution. In order for this to give you a decent image, you need either to have a long exposure time or to use very sensitive film. I suppose that using even a large mesh grid would not be satisfactory, but if it is, then that may also stabilize your specimen.
Many solvents leave a residue.
This is guaranteed to make them clean and hydrophilic. Put the film on the DULL side of the grid, which is smoother on the fine scale and offers better adhesion. One drop dried onto each grid before applying the coating film. Put on the carbon from a carbon arc at an angle to the grid, on the NON coated side, so the carbon forms a film connecting the bars to the film. Rotate the grids 180 degrees and put on another coat.