All of your experiments are correct! PEG based exosome isolation kit will co-pellet tons of hydrophobic proteins and HDL/LDL nanoparticles etc in serum or plasma. All parts will stick each other and it will be difficult to suspend. If you apply your sample serum or others to column based isolation kit, your result will be totally different! Contact me if you need further information : info@evomicscience.com
Best,
John