Duplicate SetMaterialAttributes nodes will be missing attribute connections on the node itself, but in the properties tab they will show up.
Found in 4.19 CL# 4033788, 4.20 CL# 4369336, 4.21 Preview 4 CL# 4516095, 4.22 CL# 4531805
The node will be missing the attributes on the node, however in the properties panel they show up. Additionally if you try to delete them it causes the editor to freeze.
Attributes would not be missing from the duplicated nodes and deleting nodes would not cause a freeze.
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-66150 in the post.