Unfortunately, I think the answer should be: Don't use a VeraCrypt container with Dropbox, at all.
According to https://www.veracrypt.fr/en/Modes%20of%20Operation.html
The mode of operation used by VeraCrypt for encrypted partitions, drives, and virtual volumes is XTS.
In 2010, XTS mode was approved by NIST for protecting the confidentiality of data on storage devices . In 2007, it was also approved by the IEEE for cryptographic protection of data on block-oriented storage devices (IEEE 1619).
However, Dropbox is not a regular "storage device" or "block-oriented storage device"!
In conclusion, as long as VeraCrypt is using XTS, it shouldn't be used with Dropbox. Also, see this question Is it safe to have a TrueCrypt container file synced with DropBox? as well as the blog post You Don't Want XTS.
To quote from the latter mentioned blog post:
Remember that disk encryption is designed to counter an attacker with very limited capabilities. That’s why it falls to “Evil Maids”: the threat model doesn’t really accommodate attackers with multiple bytes at the (physical) apple. But whatever margin of safety XTS gets you on physical media probably goes out the window when you stick a Truecrypt volume on Dropbox. From the vantage point of Dropbox, attackers have far more capabilities than the XTS designers planned for.