shower drain - is this gap normal?

[Dgold]

Below are two pictures of my 2nd floor shower drain. Is this gap supposed to be there, or should there be some sort of o-ring / gasket / caulking in there?

I've cleaned this up with Bleach/Water, then Bar Keeper's Friend using a stiff brush. It's not fully cleaned, but I've uncovdered this gap, and am wondering if it should or shouldn't be there, or if I need to seal it up.

I have some sort of leak which is staining the ceiling of my 1st floor kitchen. Fortunately, we've got other bathrooms, so we've been able to not use it for several days now, but I'd prefer not to open up my ceiling to fix the drain if at all possible.

Lastly, if I remove the grout around this drain, is it replaceable from the top? I might even have an extra sheet of tile.

Thanks in advance.

 

[JohnfrWhipple]

Looks like you have a clamping drain and perhaps a hot mop shower waterproofing system.

Not familiar with that drain but if you do have a hot mopped shower then you most likely have 1.5"- 2" of mortar above your hot mop. A O ring would not improve the function of the drain if this is so but might keep things a little cleaner. If you have staining from this shower then perhaps you have a leak some where.