For both the thick and thin version of the straight steel pole w/ head/foot, the texture of the foot part turns transparent if a block is placed on top of the pole. See screenshot:
https://imgur.com/a/o3tviuU

Hmm, looks almost like culling. Gonna risk a glimpse at the weekend.

Ya, was culling the model. Fixed, scheduled for the next beta at the weekend.

Dang it, forgot to release merge that in 1.15. Now it's fixed in 1.16 already, but for 1.15 it will be then in v1.1.2-b1.

Closing this one directly, I don't expect inconsistencies here, as only model files are affected (it's gonna work ;)).