[Python] Issue sending data from raspberry pi to phone app via bluetooth using python

Just having an issue with sending data collected from sensors in an excel sheet on the raspberry pi to a mobile phone device. The code works but its not consistent and there is a lot of connection dropping/ failures.

The whole system works as RaspPi collects sensor data -> Data is stored in spreadsheet -> Phone connects to bluetooth module connected to RaspPi -> Phone sends command over bluetooth to ask for data to be sent line by line

Could anyone see a problem with how I've coded this and recommend fixes or alternative ways to code this?

Bluetooth connection made using the import serial library

if __name__ == '__main__':

path = r"/home/pi/Scans/"
scans = os.listdir(path)
ser = serial.Serial('/dev/ttyS0', 115200, timeout=1)
ser.flushInput()
ser.flushOutput()

while True:

line = ser.readline().decode('UTF-8').rstrip()
ser.reset_input_buffer()

############## Request scan list #################
# Command = scans
if ('scans') in line:
ser = serial.Serial('/dev/ttyS0', 115200, timeout=1)
ser.write(('[').encode('UTF-8'))
filelist = [ f for f in os.listdir(newpath) if f.endswith(".csv") ]
for f in filelist:
with open((newpath + '/' + f), 'r', encoding="utf-8", errors="ignore") as scraped:
final_line = scraped.readlines()[-1][0:3]
if (',') in final_line:
final_line = final_line[0:2]
ser.write(('[' + str(f) + ', ' + str(final_line) + ']').encode('utf-8'))
ser.write((']\r\n').encode('UTF-8'))


############## Select scan number #################
# Put as many as necessary

if ('01') in line:
number = '01'
if ('02') in line:
number = '02'
if ('03') in line:
number = '03'
if ('04') in line:
number = '04'
if ('05') in line:
number = '05'
if ('06') in line:
number = '06'
if ('07') in line:
number = '07'
if ('08') in line:
number = '08'
if ('09') in line:
number = '09'
if ('10') in line:
number = '10'

############## Request file #################
# Command = download
if ('download') in line:
if number !=0:
ser = serial.Serial('/dev/ttyS0', 115200, timeout=1)
with open("/home/pi/Scans/Scan " + number + ".csv", mode = 'r')as file:
csvFile = csv.reader(file)
ser.write(('[').encode('UTF-8'))
for lines in csvFile:
time.sleep(0.01)
ser.write((str(lines) + '\n').encode('utf-8'))
ser.write((']\n').encode('UTF-8'))

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