In a machine with  large number of slime blocks powered by pistons, on the 1.16.201 version, slime block textures disappear while the blocks are being moved by pistons.  This is on the Windows 10 version with only the default texture pack enabled.  Video card is a RTX 2070 (ray tracing is off) with the NVidia 457.51 driver.

Repro: 

• When slime blocks are being pushed by pistons the textures will flash white until the blocks stop.  
• Was able to repro in a creative world pushing a single slime block with a single piston.
• Note that none of the other block textures (such as the redstone blocks being moved by the pistons) seem to be affected by this.