monitor arm keeps tilting down

KERDOM Ergonomic Office Chair, Mesh Computer Chair, with Lumbar Support, Rotatable, Reversible Armrests, Height Adjustable

KERDOM High Back Office Chair, Reclining office chair, w/Flip-Up Arms, Multi functional adjustable Desk Chair, Ergonomic Lumbar Support, 400 lbs

EUREKA ERGONOMIC Galene, Faux Leather Office Chair

Emma and Oliver Mid-Back Black Mesh Multifunction Ergonomic Office Chair with Adjustable Arms

Emma and Oliver High Back Executive Swivel Office Chair with Metal Frame and Arms

Flash Furniture Mid-Back Executive Swivel Office Chair with Metal Frame and Arms