Problem with graphic card

"The video signal from the CPU has two different GPU logic paths going to the IG or via the DG, then the signal has three different paths by default the internal display via the internal DisplayPort (iDP) connection, then you have either the HDMI port or lastly the Thunderbolt ports treating the connection as a DisplayPort connection.

Depending on what you’ve set within the Energy Saver control panel if you’ve checked off the Automatic graphics switching. This sets the IG as the preferred graphics services unless the application tells it otherwise. Some actions within the startup settings will also force the IG as the preferred graphics services. Otherwise the DG will be used if available (the IG only models don’t offer this setting).

OK, now that we have a handle on how this all works we can try to figure out whats happening with your system.

Which are you using for your external display? The HDMI connection or the Thunderbolt connection?"

"If you don’t want any problems when you use dedicated graphics card (AMD), you MUST use only the default display settings for your retina display (i.e. 1440x900, it may also be designated as 2880x1800 in your computer since it’s quadrupled by using factor 2x2 for each figure, due to “retina” specification).

You can use “more space” or “larger text” options in Mac’s own display settings only when you switch off the dedicated graphics card.

Hope this helps.

Update (12/02/2018)

I can add one more additional thing to resolve the problem: You can disable switching (between dedicated graphic to integrated graphic) in the energy saver preferences, and this issue may be totally gone. The battery life may get shorter of course, since you are no longer saving energy (using dedicated graphics all the time).

By the way how do you know (how do you make sure) that it uses integrated graphic all the time ? I mean did you find a way to switch off the dedicated graphics card (such as https://gfx.io) ? I’m asking this because you say there is no problem when it uses only integrated graphics, however this is not normally possible by original native apple software. Either you have dedicated graphics all the time if you disable energy saving feature, or you have intermittent switching between dedicated graphic and integrated graphic during use. My guess is, the time periods you don’t have any problem are when you are on dedicated graphics all the time."