It appears there is a bug. I am able to replicate the problem with this flow
The dropdown node returns a number instead of a string. I have a vague recollection of this being fixed ages ago, perhaps somehow it has returned.
That is with node-red 1.3.4 and dashboard 2.29.0
If I hard code the options into the dropdown node then it is fine.
@knolleary should I submit an issue for this?
[{"id":"f2042e3d.90c87","type":"ui_dropdown","z":"84405ff5.25fa6","name":"","label":"","tooltip":"","place":"Select option","group":"807b5c7.909b2a","order":12,"width":0,"height":0,"passthru":true,"multiple":false,"options":[],"payload":"","topic":"topic","topicType":"msg","x":280,"y":1140,"wires":[["92dcc263.ad2058"]]},{"id":"b25f37ba.1a80c","type":"inject","z":"84405ff5.25fa6","name":"options: [{\"33640.20\":\"33640.20\"},{\"35789.30\":\"35789.30\"}]","props":[{"p":"options","v":"[{\"33640.20\":\"33640.20\"},{\"35789.30\":\"35789.30\"}]","vt":"json"},{"p":"topic","vt":"str"}],"repeat":"","crontab":"","once":true,"onceDelay":0.1,"topic":"","payloadType":"str","x":280,"y":1080,"wires":[["f2042e3d.90c87"]]},{"id":"92dcc263.ad2058","type":"debug","z":"84405ff5.25fa6","name":"","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"true","targetType":"full","statusVal":"","statusType":"auto","x":430,"y":1140,"wires":[]},{"id":"807b5c7.909b2a","type":"ui_group","name":"Group 1","tab":"4b4528d.4e9cad8","order":1,"disp":true,"width":6},{"id":"4b4528d.4e9cad8","type":"ui_tab","name":"Example","icon":"dashboard","order":8,"disabled":false,"hidden":false}]