import re
strs = ['-line[8qWWQ5-swd-WER-DWDS]]<-SUCCESS#[14][MY_SAMPLE_TEST]', '-line[8qWWQ5-swd-WER-DWDS]]<-SUCCESS#[4][MY_SAMPLE_TEST2]', '-line[8qWWQ5-swd-WER-DWDS]]<Failed#[17][[14]SERVERERROR(TYPE-241)']
rx = re.compile(r'#(?:\[+\d+]+)*\[*([^][()]+)')
for s in strs:
m = rx.search(s)
if m:
print(m.group(1))
aW1wb3J0IHJlCnN0cnMgPSBbJy1saW5lWzhxV1dRNS1zd2QtV0VSLURXRFNdXTwtU1VDQ0VTUyNbMTRdW01ZX1NBTVBMRV9URVNUXScsICctbGluZVs4cVdXUTUtc3dkLVdFUi1EV0RTXV08LVNVQ0NFU1MjWzRdW01ZX1NBTVBMRV9URVNUMl0nLCAnLWxpbmVbOHFXV1E1LXN3ZC1XRVItRFdEU11dPEZhaWxlZCNbMTddW1sxNF1TRVJWRVJFUlJPUihUWVBFLTI0MSknXQpyeCA9IHJlLmNvbXBpbGUocicjKD86XFsrXGQrXSspKlxbKihbXl1bKCldKyknKQpmb3IgcyBpbiBzdHJzOgoJbSA9IHJ4LnNlYXJjaChzKQoJaWYgbToKCQlwcmludChtLmdyb3VwKDEpKQ==