i am also seeing fishy behaviour suddenly related to the scala_js module, but it seems to be related to the engine in some way... perhaps things getting double loaded (in our repo, so not reproducible probably):

$ ./pants --enable-v2-engine test 3rdparty/::
...
Exception message: TaskRegistrar 'node' with action NodeResolve_resolve_node depends on scala_js_binaries from task ScalaJSLink_resolve_scala_js_link which is ordered after it in the 'resolve' goal:
	[0] 'ivy' IvyResolve_resolve_ivy
	[1] 'ivy' IvyResolve_resolve_ivy
	[2] 'go' GoFetch_resolve_go
	[3] 'scala-js-compile' ScalaJSZincCompile_resolve_scala_js_compile
	[4] 'scala-js-link' ScalaJSLink_resolve_scala_js_link
	[5] 'node' NodeResolve_resolve_node
	[6] 'go' GoFetch_resolve_go
	[7] 'scala-js-compile' ScalaJSZincCompile_resolve_scala_js_compile
	[8] 'scala-js-link' ScalaJSLink_resolve_scala_js_link
	[9] 'node' NodeResolve_resolve_node