I purchased some bee houses to attract bees, mason bees etc.
The bottom one was purchased with leaf cutter bees. It worked well and most of the straws were capped over after they were done, but over the winter something got into them and it appears they've been destroyed. Even some of the straws appear to have been pulled out.

I have no idea what it could be, (I'm guessing birds) but I've never seen it happen.
The top house had many of the holes capped off at the end of the summer and all of those were apparently destroyed.
I was thinking of using bird netting, like people do over strawberries or cherry trees, but I"m not sure it's birds.

Has anyone had similar problems?

After research I learned that this is caused by birds. So I made some bird guards out of 1x1 inch wire mesh in order to keep the birds from getting at the bee house, disturbing the nesting tubes and killing the bee larva. In this case, leaf cutter bees. There appears to be some bees still in some of the nesting tubes, so I'll see if they emerge in the warmer weather.
I built a new bee house for both early mason bees for apple tree pollination and leaf cutter bees for midsummer pollination. This new bee house also has a bird guard in place and a door in front to place purchased bee cocoons.

Great job!

Your new bee house is very professional. I have seen many ways to build homes for many different types of bees on you tube. Yours is gorgeous and you are very talented . Are you taking any orders?.... just kidding. I wouldn't mind have one of those in my garden.
Thank you for showing how you take care of the bees in your area. This has likely sparked new interest for many of us looking for ways to support bees.

Thank you bumplbea.
The straws used for the nesting tubes I found online, they're paper but very rigid. I have two sizes; 6mm for leaf cutter bees and 8mm for mason bees. Mason bees are earlier and good for apple blossom pollination. Both are due to arrive this week. The leaf cutter bee nesting block will be kept cool until May. Bottom right are bamboo stakes cut to length and the soft centers drilled out.
Photo is last years leaf cutter bee nesting tubes. The very green leaf caps are newly made by the bees after only a week. Our harvest last year was the best ever, with the pollination causing better fruit set, particularly with squash, pumpkins etc.