Hi, Kevin
These are the outcomes of the two commands after a regular termination of the programm, i.e. execution until the last line. Pls see below.
It will be difficult to produce a 'reproducible example' because not only has the program almost 2000 lines by now; as soon as I klick the red STOP-button, the program stops, RStudio remains inaccessible for a few seconds - and then, suddenly, the message "R session aborted" appears, see pic.

I can only get rid of this message by pressing the "Start New Session"-button shown and at the same moment everything is lost. I'm unable to recover any diagnostic information provided in principle by RStudio help facilities.
sessionInfo()
R version 3.5.1 (2018-07-02)
Platform: x86_64-w64-mingw32/x64 (64-bit)
Running under: Windows 10 x64 (build 17763)
Matrix products: default
locale:
[1] LC_COLLATE=German_Germany.1252 LC_CTYPE=German_Germany.1252
[3] LC_MONETARY=German_Germany.1252 LC_NUMERIC=C
[5] LC_TIME=German_Germany.1252
attached base packages:
[1] stats graphics grDevices utils datasets methods base
other attached packages:
[1] ggplot2_3.0.0 keras_2.2.0.9000 tensorflow_1.9
[4] reticulate_1.10 RevoUtils_11.0.1 RevoUtilsMath_11.0.0
loaded via a namespace (and not attached):
[1] Rcpp_0.12.18 pillar_1.3.0 compiler_3.5.1
[4] plyr_1.8.4 bindr_0.1.1 base64enc_0.1-3
[7] tools_3.5.1 zeallot_0.1.0 jsonlite_1.5
[10] tibble_1.4.2 gtable_0.2.0 lattice_0.20-35
[13] pkgconfig_2.0.1 rlang_0.2.1 Matrix_1.2-14
[16] rstudioapi_0.7 bindrcpp_0.2.2 withr_2.1.2
[19] dplyr_0.7.6 grid_3.5.1 tidyselect_0.2.4
[22] glue_1.3.0 R6_2.2.2 purrr_0.2.5
[25] magrittr_1.5 whisker_0.3-2 scales_0.5.0
[28] tfruns_1.4.0.9000 assertthat_0.2.0 colorspace_1.3-2
[31] labeling_0.3 lazyeval_0.2.1 munsell_0.5.0
[34] crayon_1.3.4
reticulate::py_config()
python: C:...\AppData\Local\conda\conda\envs\r-tensorflow\python.exe
libpython: C:/.../AppData/Local/conda/conda/envs/r-tensorflow/python36.dll
pythonhome: C:...\AppData\Local\conda\conda\envs\R-TENS~1
version: 3.6.6 |Anaconda, Inc.| (default, Jun 28 2018, 11:27:44) [MSC v.1900 64 bit (AMD64)]
Architecture: 64bit
numpy: C:...\AppData\Local\conda\conda\envs\R-TENS~1\lib\site-packages\numpy
numpy_version: 1.14.3
keras: C:...\AppData\Local\conda\conda\envs\R-TENS~1\lib\site-packages\keras_init_.p
NOTE: Python version was forced by use_python function
ADDENDUM 2019-07-02
Only quite recently I made the following observation: The session abort picture only appears several seconds after the program has stopped, if during this time interval I hit the ENTER key, the following message appears in red: "Unable to establish connection with R session." Since this happens only since the above mentioned RStudio update, would it perhaps be helpful to re-install one of the older versions? (The one I replaced was 1.1.456 - where could I download this version?)