That looks like quite an extreme example!
What sugar(s) are you using, and how much? The solubility of sucrose, glucose, and fructose differs.
FWIW, it's fairly common to see liquid sucrose supplied at 67 Brix in ambient IBCs/tankers, with storage at circa 10-20C. Fructose is more soluble, but glucose less so, and you can see crystallisation problems in that more readily.
What acid are you adding, and how much? Just worth some consideration as I've seen acids precipitate out of solution too. It's a well-known issue with tartaric acids for example, to the extent that many grape processors and wine makers force it to happen during processing so it doesn't happen later.
As an easy way to rule out acid precipitation you can taste some of the crystals after rinsing the sauce off them - if they're sweet then it isn't the acid that is crystallising.
What is your storage temperature? Solubility decreases with decreasing temperature, so if these are intended to be chilled rather than ambient then that is more of a challenge.