Is this not the most sh**ty thing you have seen on a cheap chinese mini lathe tailstock, or is this all too common?
Left side quarter inch gap between bed and base?
Ironically the height is about center, so making the triangle bigger to make it flush will lower the center height by a quarter inch.
I believe the best bet here would be to mount a steel or brass 1/8in or so plate under everything but the triangle area to make it level.
That is of course just a short term solution instead of making a new bottom plate correctly to begin with.
Consider case closed, found another user who just replaced the whole bottom plate.
It turns out to be less work to just use steel instead of cast iron and hope the vibration plays well with titanium.