Hi womandi,
I cannot be certain why you may have started to encounter this behavior recently, but I am inclined to agree that it is most likely due to a conflict between the original formatting code used for the descriptions of the item(s) and the new formatting code that is being introduced when making the changes you described through the editor on the eBay Revise your Item form.
We did not make any changes to our description editor around when you began encountering this issue, but the one thing that comes to mind which could have led to a change in the formatting code produced when creating your listings through Auctiva is if you just enabled our new description editor (called the Design Editor 2.0) from your Account Preferences.
I do not anticipate this is a result of something we will be able to *fix*, but we will be happy to look into the situation further for you if you file a support case and provide us with the details of one or two specific listings for which you encountered this problem.
I attempted to reproduce this issue using a test listing posted through Auctiva using bold description text set to size 16 Arial, but I did not encounter anything like what you described when I deleted a word within the text and typed a new word in its place through the eBay Revise your Item form.
It also may be a good idea to contact eBay's Customer Support team to see if they are aware of any technical issues with the description editor on the Revise your Item form which may explain the behavior you are encountering.
Janne,
I am not sure what may be causing the errors you reported receiving when attempting to edit 50 listings at a time, but I suspect our system may be timing our when attempting to process your request. I see that you filed a support case about this issue earlier today and we will follow up with you about the issue through that case.
Assuming you are still encountering this issue, you may want to try reducing the number of listings you are attempting to edit in each batch and see if you can complete the revisions you wish to make to the BIN prices in your listings that way.
-Mike