Here are the steps I follow to reproduce the issue:

Open sim axis_mm config.
Edit a copy of axis.ngc example file and remove G64 in line number 10.
Run the program. Observe liveplot – TP rounds the corners.
Execute G61 in MDI.
Run the program again – TP does not round the corners.
Hit F1 (E-stop).
Run the program again – TP rounds the corners.

This issue might influence similar behaviour after startup, when Estop HAL pin is used and in INI:
RS274NGCSTARTUPCODE = G61
or
RS274NGCSTARTUPCODE = G64 P0.1 Q0.001
Do not forget to open modified axis.ngc file while testing.

This is what I expected to happen:

G61 / G64 mode retained, including G64 P and Q parameters.

This is what happened instead:

G61 / G64 modes are lost.

Using LinuxCNC 2.7.7