diff --git a/Known-issues.md b/Known-issues.md
index ac52c2f..3d272c0 100644
--- a/Known-issues.md
+++ b/Known-issues.md
@@ -14,6 +14,12 @@
  * If game crashes with `(AcLayers): (unknown): NotifyShims` on the stack - this was a bug in d3d9.dll bundled with ifs_layeredfs, please update to v3.8 or higher. See https://github.com/mon/ifs_layeredfs/issues/11.
  * Unless you know **exactly** what you are doing (e.g., running on an arcade cab) - do not use the `-exec` option. Using the `-exec` option will result in the game-specific hooks being disabled, which means you'll see weird crashes and various features not working properly.
 
+### I/O
+
+ * `Insert Coin` action is not implemented in all I/O. Some older systems omit this; you should just be using the `Service` button anyway.
+ * `Insert Coin` and `Service` may be prevented due to "coin strip" - some data release groups in the past ripped out the code that handles coins to discourage people from running data in real arcades. Get a clean DLL to fix this, or enable Free Play instead.
+ * In a real arcade, a "coin blocker" physically prevents coins from being inserted. This would be enabled by the game if you set shop closing hours in the test menu.
+
 ## OS Support
 
  * Officially supported OS versions: Windows 7 and up.