Neighbor Parked Conex Boxes On Easement, Will Not Move

Hello everyone,
I live on ~1.3 acres in Kitsap County, WA. I access my house across a public easement on the southern 15' of my westward neighbor's property line. That easement extends through my property and the neighbor's to my east. My eastern neighbor's property is undeveloped; I rarely see them. Another neighbor owns an abutting 5 acres directly to the south of all three of us. Last summer, the southern neighbor (S) and eastern neighbor (E) got in a dispute about E felling trees along the southern part of the easement to access their property. This would apparently last all summer, and S repeatedly told me they were pursuing legal action against E for cutting down the trees. I decided to stay out of it and left for the summer for work.
Last August, my spouse called to tell me that E had parked three Conex Boxes on our part of the easement. When I got home, I caught E as they were leaving their property and asked about the boxes. They informed me the boxes were only there temporarily and that they would have them moved east to their property soon. S told me E put the boxes there to spite them. I didn't mind because (1) the boxes were off in the woods out of eyesight; and (2) they would be gone soon. Additionally, I wanted to stay out of the dispute.
Well, E never moved the boxes. I called them in March of this year, and we agreed that the boxes would be moved by May 30th. I called to confirm the move mid-May and once again today, but E will not return my calls. We are getting our house ready to sell and need the boxes to vanish.
My instinct is to have them towed away. Something like that must exist for Conex boxes, but I don't want E coming after me for taking their property. Additionally, I don't want to pay thousands to have them moved. So, assuming there is someone willing to take the boxes at the E's expense, can I avoid liability for doing so?
Thank you all for your time and effort. A link to a better description of the property follows: https://imgur.com/a/NR3Ua1N
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