When using the contain node for an array there is a delay is getting a proper warning to show under certain conditions. This issue occurs when a pin for the bottom is connected before the array is. If the array is connected first you cannot add a mismatched type to the bottom.
In 4.14 even when you restart the project the pin stays connected with no error but if you disconnect the pin you cannot reconnect it. In 4.15 and later versions, An error is created, but only after the editor is restarted, The array should be able to connect at all, or the error should appear after the compile.
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