Since you did not say, I am guessing from a previous post that you are using a Picaxe 18M2
If you cannot figure out a way to place the suggested resistor, then you might try placing a "Low C.3" as the very first line of the program. This will set the sertxd Pin as an output and make it low. Then use delay of at least 1 second before sertxd is used in the program.
A scope on the sertxd line shows a short positive glitch on the sertxd Pin when the terminal program opens and subsequently opens the com port. The resistor suppresses this glitch.
The diagram below shows how I might place the resistor.
View attachment 18800