Many problems are caused by broken files in the game's <tt>Content</tt> folder (especially if you use XNB mods). You can reset your game files to fix that. If you use any XNB mods, they'll be removed. SMAPI mods won't be affected.
# Reset your game files (see instructions [https://support.steampowered.com/kb_article.php?ref=2037-QEUH-3335 for Steam] or [https://support.gog.com/hc/en-us/articles/212807405 for GOG Galaxy]).