Clearing GL accounts in multiple currencies

We have a situation in ourt GL we are trying to avoid.  We have certain GL accounts in a Canadian ledger that get debit amounts to the account in both USD (entered currecny ) and CAD (function currecny).  The offsetting credit amounts to the account come only in CAD.  These accounts are clearing accounts.  The CAD amounts are clearing fine.  The issue is that USD amounts just build up a USD balance.  The accounts are NOT Revaluation accounts so there is no risk of improper Gain and Loss being recorded.  Is there any other risk in letting these accounts continue