Schemes for international geocoding really shouldn't shrug off this altitude problem. When you say third floor, are you using 0-indexing, or 1-indexed floors as in the US?

See "What about floor numbers and apartment numbers?" in their FAQ: https://plus.codes/faq

It’s quite likely that you already have a better working street address in that situation. If not, the address could be something like

Name +code, city apartment 3A