Create new file defaults as folder name, cannot change

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FastHub Version: 4.6.7
Android Version: 7.0 (SDK: 24)
Device Information:

• Manufacturer: samsung
• Brand: samsung
• Model: Galaxy S6

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Hi
Create a new file in folder _posts. New blank file is opened with default name "_post". Edit file and change file name to Jekyll-friendly 2019-09-12-new.md get error messge "_posts is not a file". Tried renaming with _posts/ folder as a prefix and that didn't work either.
What is wrong?