cam_inst.read() returns past image

edit

I'm capturing and processing images iterately with in time interval. (3mins) code is written with python3.6, and run on Raspberry-pi (OS is Raspbian)

Whenever I run the code, it stop showing this Error.

ValueError Occured in del_ext/ del_ext skipped
OpenCV Error: Assertion failed (dsize.area() > 0 || (inv_scale_x > 0 && inv_scale_y > 0)) in resize, file /home/pi/opencv/opencv-3.4.0/modules/imgproc/src/resize.cpp, line 4045
Traceback (most recent call last):
  File "runpi.py", line 264, in <module>
    run(3.5,model_list)
  File "runpi.py", line 234, in run
    mat = temp.match(model_list)
  File "runpi.py", line 184, in match
    self.__resize(model.get_m_inform())
  File "runpi.py", line 147, in __resize
    self.mask = cv2.resize(self.mask, None, fx=reratio, fy=reratio, interpolation = inter_method)
cv2.error: /home/pi/opencv/opencv-3.4.0/modules/imgproc/src/resize.cpp:4045: error: (-215) dsize.area() > 0 || (inv_scale_x > 0 && inv_scale_y > 0) in function resize

And I found out that

• It looks this error occurs only when running for more than an hour.
• Recent taken images are out of date and the time gap is getting bigger with time pass

It looks kind of Video siganl is stored in RAM on R-pi and .read() returning out-dated image in RAM

What could be the solution for this problem?

Here is main part of the code

   def run(interval,model_list):
        cam0 = cv2.VideoCapture(0)  #Only cam0 is used. cam2 is just to record.
        camdir = "/home/pi/capstone/cam0/"
        cam2 = cv2.VideoCapture(1)
        cam2dir = "/home/pi/capstone/cam2/"
        runNo = 0
        acc_list = list()
        error_list = list()
        end = False
        while(end == False):
            print(runNo,"th run")

            img_name = "%s.jpg" %runNo
            frame, res = cam0.read()   #`res` is the image which will be processed
            cv2.imwrite(os.path.join(camdir,img_name),res)
            _ , cam2pic = cam2.read()
            cv2.imwrite(os.path.join(cam2dir,img_name),cam2pic)
            try:
                temp = Real(res)
                mat = temp.match(model_list)
                acc_list.append([mat,runNo])
                print("Accuracy=", mat)
            except ValueError:
                acc_list.append(["ValueError",runNo])
                error_list.append(["ValueError",runNo])
            except AttributeError:
                acc_list.append(["AttributeError", runNo])
                error_list.append(["AttributeError",runNo])
            except SmallObjectError:
                acc_list.append(["SmallObjectError", runNo])
                error_list.append(["SmallObjectError",runNo])
            runNo = runNo+1
            endNo = 40
            if(runNo/2 > endNo):
                end_check(res, end)
            elif(runNo > endNo):
                end = True
            sleep(interval*60)

        with open("acc_list.txt", "w") as output: #records for tracking errors
            output.write(str(acc_list))
        with open("err_list.txt", "w") as output:
            output.write(str(error_list))
        cam0.release()
        cam2.release()

    run(3.5,model_list)