Victorian house floor issues

newfoundglory

Hello

Recently moved into a Victorian (1900) house, just about detached so air-bricks all around, which has a few odd floor issues.

Neither my surveyor (or the sellers surveyor prior to that) found any significant cracking, current settlement/subsidence or structural movement + no indication of foundation problems. Floors were indicated as apparently level and firm. One survey suggests there are "doubled-up" floor joists (upstairs?)

Although I didn't notice on the viewings, some stairs and the bathroom are obviously sloped. some of the door frames are very wonky upstairs (although the floors basically straight in most cases). one of the bedrooms is slightly sunken in the middle of the floor and sounds like a few lose boards (clunking, not creaking)

The house was refurbed by the seller and the floors covered in carpet/underlay, so inspecting not easy now.

My biggest concern is the hallway, which again seems firm, but very lumpy and you can feel either raised or sunken boards under foot and at the bottom of the stairs.

I have become concerned at what I might find under the carpet, but did find an old for-sale image of the living room;

https://imgur.com/a/NWTg4t7

Is this an original floor or not? Not all the boards look the same...
Grateful for any thoughts and experiences on victorian floor issues and best ways to go about investigating