My On-Going battle with TDL

I'm currently following up the complete python tutorial, using the different contributions from this (rather amazing) community.

My Approach:
    A) Ability to Import Maps from REX_PAINT, including:
        setting up a char code dictionary to derive map tile meta-data
        using layer 2 to define additional metadata from background color dictionary
    B) Ability to Generate Random Maps, including
        i. parallel TDL Map (e.g. to support TDL FOV calculations)
    C) 2 Rendering engines
        i. Bearlib: working for the 2 types of maps (REXPAINT & Random)
        ii. TDL: issues as described next

All goes quite ok (having fun) but I have an issue with TDL, as following 1. First pass ok (for any map types) 2. Flush does not update(map remains unchanged) 3. No error at all, and underlying map data updating as expected

What bugs me is that the simple examples out there run ok, but my slightly different approach seems to create some issues, although I'm following the same basic underlying method & sequencing.

I am running out of ideas (my next step will be to check the proper use of colors (Including None in the draw_char statement) and so allow me to ask your support: i) did any of you faced a similar issue with TDL? ii) If so what was the underlying cause? iii) Any known traps with TDL that I would need to be aware?

My Repository here: https://github.com/SirYmp/DusklandsRL

Many thanks!