Probably a number of coincidences. As to the SD card, sounds like it's gone bad, try a different one!

Over at PF there's a thread which started mid December about an anticipated firmware update for the K-1 .
So Pentax will be at the NEC in March, presumably they'll have something to show?

Re the background, rather than blur it, what about darkening it down?

Tried eBay? eg https://www.ebay.co.uk/itm/Pentax-67-Medium-Format-6x7-Camera/332529851397?hash=...

No camera actually requires a polarizer. They are designed to cut out unwanted reflections and can darken the sky depending on direction and lighting conditions. Sure you're not thinking of skylight/UV filters? As with any filter you get what you pay for, but that doesn't mean some of the cheaper ones aren't worth considering.
As to using filters for monochrome film, people often used a coloured filter to give a better contrast for some subjects and lighting conditions.
Skylight/UV filters are often used for colour slide film to cut down the bluey haze effect and some use them as lens protectors with digital.
Some digital users like to use graduated filters which can help darken bright skies. These are often square in shape but round ones do exist.
What are you wanting to achieve with your intended filter purchase as that might help pointing you to the right thing and stop you getting something you don't need!? The age of the filter is the least of the considerations and there are often excellent condition second hand old filters in camera shop bargain bins and eBay at a fraction of the cost of new ones which will suffice just fine. But you need to know what you want!

Can you define modern and older?!
I still use Polarizers I purchased in the 1970's and they work just fine.
I suspect what you mean by 'modern' are those described as circular. With some brands using those can make a difference (when indeed the non-circular may not work as expected) but I haven't noticed any problem with non-circular on my Pentax DSLRs. The circular description doesn't refer to the shape of the filter but the way in which light passes through it.

As to both the Pentax & Tamron 15-30's being the same or not is not for me to say, but looking at the optical diagrams for both they seem remarkably similar to be completely different lens designs.
Make up your own mind.
(Images linked from manufacturers web sites.)

Pentax



Tamron



My conclusion,"if someone glibly repeats the falsehood that the Pentax 15-30mm lens is just a rebadged Tamron" I might be tempted agree with them based on those diagrams.

I didn't spot that, in which one and where? Presumably in the first two minutes!!

Oh well, perhaps it's given someone some inspiration!

Is this to get inspiration for this week's weekly comp entry?