Nextion serial problem

Hi.

For a while now I have been using a Nextion display with a Wemos D1 mini.
They communicate with each other using SoftwareSerial.
I have had no issues until I recently updated from Arduino IDE 1.6.9 to 1.8.5
Now when I download my project to the Wemos D1 mini using the 1.8.5 IDE I end up with erratic communications to and from the Nextion display.
When I download using the 1.6.9 IDE all works fine.
Does anyone have any ideas what the problem might be?

Works fine with esp8266 2.4.0-rc2 library but not with esp8266 2.4.0 or esp8266 2.4.1
SoftwareSerial: was updated to 3.3.0 in the esp8266 2.4.0 update.
Any ideas on what could be causing issues in this update.