WooCommerce Multicurrency currency problem

Having a major problem with the currency switcher. My store is CAD based. All prices are entered in CAD. Have it set up for user can switch to USD. Currency conversion works great switching to USD but if they switch to USD and back to CAD, the original CAD price gets messed up. It looks like it is doing a double conversion or something. As a result I have overcharged a couple customers already. Can anyone assist?

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