As far as I remember, RPI engineers wrote on the forum that if you add more than 512 Mb to the config.txt GPU file (I may be wrong in the numbers), then Raspberry may not load correctly.
As I understood from the messages of the programmers of the developers, in the fourth version of Raspberry there is no need to "expand" the video memory in the configuration file, since working with video memory is now carried out somewhat differently than before.
However, other programs (Kodi) may need the GPU memory option, therefore it is recommended to set the minimum value. Here on the forum there was a thread dedicated to this issue, it can be found.
I am glad that your problem has been resolved!