It's possible to have seed in your paint ,, but for starters every painter should filter their paint very well especially before attempting a multilayer paint and also To be painting a colour that nice and use old clear is rediculous ,, and filtering would lose all the lumps anyway ..,,
You can have many problems with solvent traping and solvent boil if not applied properly even not mixed properly ,, there R many problems and will usually be a result of poor paintin ..