I am taking sections of formalin-fixed, paraffin-embedded rodent brain 5 um thick using a microtome. I chill the blocks ahead of time and put them into a 42 C water bath after sectioning. I remove the slides from the bath using charged slides, but have recently been running into the issue that the sections are forming wrinkles and bubbles in the water bath. I've attached images to show the issue. I've tried adjust the temperature both up and down, added a drop of dish soap prior to filling the water bath, and thoroughly cleaned the water bath. I had not run into this issue until I started using this water bath. Has anyone seen this issue before, and how did you resolve it?