I think there's a bug in the flowing of text from one frame to another. I attach a test file to demonstrate this.
1. Click inside the 3-column text frame.
2. Click on the little (it could usefully be bigger) orangey-red triangle on the frame's right-hand edge. The "new text frame" cursor appears (T in a box).
3. Attempt to drag a new text frame. If it works, move to the new text frame, click inside that, and keep repeating steps 2 and 3.
4. For me, this will sooner or later cause Publisher to crash. Sometimes it happens on the first "flow out" attempt; sometimes only after 2 or 3 or 4 "flow outs" have been completed.
This is on my Windows 10 laptop:
Microsoft Windows 10 Home
Version 10.0.17134 Build 17134
Processor Intel(R) Core(TM) i7-7500U CPU @ 2.70GHz, 2904 Mhz, 2 Core(s), 4 Logical Pr...
BaseBoard Manufacturer HP
Graphics (GPU): GeForce GTX 950M
test document (bug demo).afpub
P.S. I wonder if this Text Frame bug is related to another one found by Dominik, here: