Is it just me? A few days ago it started to display red Xs everywhere:
View attachment 115942
I updated the app, but there has been no change.
In the newer version of OsmAnd for Android one can select from various colours, symbols, and shapes for one's personal Favourites aka Places. I do so myself. For example, for albuerges I choose the bunk bed symbol and for hostels and hotels and any other type of lodging that provides private rooms I choose the single bed symbol. For food stores I select the shopping cart symbol, etc. One of the available symbols is an X.
Try selecting a Favourite and then press edit. In the lower portion of the screen you should see horizontally-scrollable tabs for various categories of symbols. On my device, there are additional tabs out of sight to the right; one must drag the tabs to the left to reveal those additional tabs. Select a category tab and then select a symbol and press Save. The icon on the maps should now display the new symbol.
However, the apparent fact that many of your Favourites spontaneously changed all at the same time suggests a hiccup in the app. Being winter, your ambient air might be dry, setting the stage for a build-up of static charges on the surface of the device, which might have corrupted a file at startup. If it was me, I would close all apps, perhaps wipe down the device with a barely-water-damp cloth, let it dry, and then reboot the device, possibly several times, then restart OsmAnd and see if that fixed the problem.
None of my Favourites icons have the small downwards-pointing V-shaped feature at the bottom of the icons displayed in the image you provided.