I do not think that you can refile until the first or previous filing is processedBut in any case I wouldn't as it would confuse the issue and create more delay...
Just noticed on the CRA site that many of the tax slips from Financial Institution and Employers are not there to downloadIt may well be that CRA has a problem ...
Really looks like CRA is verifying all who submitted their Taxes in the early days ( March 19th , 20th) when it was supposed to be fixed with Capital gainsMakes...