also when adding another signature below the grid,

getting this in log 

ERROR 25 Sep 2020 10:44:13 org.joget.apps.form.service.FormUtil - jsonToFormRowSet error
org.json.JSONException: A JSONArray text must start with '[' at character 1
at org.json.JSONTokener.syntaxError(JSONTokener.java:496)
at org.json.JSONArray.<init>(JSONArray.java:115)
at org.json.JSONArray.<init>(JSONArray.java:159)
at org.joget.apps.form.service.FormUtil.jsonToFormRowSet(FormUtil.java:2372)
at org.joget.apps.form.service.FormUtil.jsonToFormRowSet(FormUtil.java:2361)
at org.joget.plugin.enterprise.FormGrid.parseFormRowSetFromJson_aroundBody30(FormGrid.java:500)
at org.joget.plugin.enterprise.FormGrid.parseFormRowSetFromJson_aroundBody31$advice(FormGrid.java:99)
at org.joget.plugin.enterprise.FormGrid.parseFormRowSetFromJson(FormGrid.java:1)
at org.joget.plugin.enterprise.FormGrid.getRows_aroundBody28(FormGrid.java:451)
at org.joget.plugin.enterprise.FormGrid.getRows_aroundBody29$advice(FormGrid.java:99)
at org.joget.plugin.enterprise.FormGrid.getRows(FormGrid.java:1)
at org.joget.plugin.enterprise.AdvancedGrid.getDisplayRows_aroundBody18(AdvancedGrid.java:209)
at org.joget.plugin.enterprise.AdvancedGrid.getDisplayRows_aroundBody19$advice(AdvancedGrid.java:99)
at org.joget.plugin.enterprise.AdvancedGrid.getDisplayRows(AdvancedGrid.java:1)
at org.joget.plugin.enterprise.AdvancedGrid.renderTemplate_aroundBody14(AdvancedGrid.java:106)
at org.joget.plugin.enterprise.AdvancedGrid.renderTemplate_aroundBody15$advice(AdvancedGrid.java:99)
at org.joget.plugin.enterprise.AdvancedGrid.renderTemplate(AdvancedGrid.java:1)

Googled and found this Add Signature Form Element as Image into Email Content.

won't work image also doesn't appear on the PDF