I was walking along a trail in primary jungle when this babbler hopped into the nest about 5 meters in front of me. I stopped and dropped to the ground, and the birds continued to build the nest despite being aware of my presence. I decided to remain there and watch. I did not go back for a tripod/video equipment as I felt it would disturb the birds. The nest was being built about 2.5 meters above the ground in a bamboo thicket. The birds were using a large dead leave that had fallen and lodged on the bamboo. The leave belonged to a Giant Macaranga tree. The nesting material they were using was predominantly dead bamboo leaves and occasional leaf skeletons/spines of leaves. Nesting material was often collected some distance from the nest site. Building was a fast activity and the frequency of visits was 2 per minute, with often one bird waiting for the other to clear the nest before going in. As far as I could ascertain there were only 2 birds involved in the nest building and the work was fairly equally shared. No calls were made while nest building. The nest was still at the early stages of development. I was concerned with their choice of nesting site for two reasons. One it was on a fairly busy trail for walkers and the birds could easily be spotted when moving (the nest itself could not be easily spotted). More importantly their choice of nesting leave was poor as I could see the nesting material falling out occasionally, even as the put more in. I expect the nest to fail.
I watched for ~15 minutes and then decided to leave so as to give the birds the space needed. Short handheld video here: https://youtu.be/0hBGQhp9TGg
Update: I returned 1 week later and as expected the site is abandoned and this nest has failed.