I'm new member of this forum, i've the same problem, i can't release with obfuscated my app.
I have jdk 1.8.0_161 and my error is:
B4A Versione: 7.80
Analisi del Codice. (0.02s)
Compilazione del codice. (0.15s)
File ObsucastorMap.txt creato nella cartella Objects.
Compilazione del codice di...